ACTIVE/PASSIVE AGGRESSIVE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Active/Passive Aggressive Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Active/Passive Aggressive Portfolio	$14	0.26%

Portfolio Statistics

Total Net Assets (000's)$87,104
# of Portfolio Holdings (Derivatives not included, if applicable)26
Portfolio Turnover Rate25%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
iShares Core S&P 500 ETF	10.3%
Northwestern Mutual Series Fund, Inc., Select Bond Portfolio	8.9%
Northwestern Mutual Series Fund, Inc., International Equity Portfolio	7.5%
iShares Core MSCI EAFE ETF	6.3%
State Street SPDR Portfolio S&P 400 Mid Cap ETF	6.3%
iShares Core U.S. Aggregate Bond ETF	5.4%
Northwestern Mutual Series Fund, Inc., Large Cap Blend Portfolio	4.5%
Northwestern Mutual Series Fund, Inc., Focused Appreciation Portfolio	4.5%
Northwestern Mutual Series Fund, Inc., Domestic Equity Portfolio	4.5%
Northwestern Mutual Series Fund, Inc., International Growth Portfolio	4.3%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	3.7%
Commodities	0.8%
Fixed Income	17.4%
Foreign Equity	26.8%
Domestic Equity	51.3%

Additional Information

If you wish to view additional information about the Portfolio, including but not limited to its prospectus, financial statements, holdings, or proxy voting information, please visit www.nmseriesfund.com.

ACTIVE/PASSIVE AGGRESSIVE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

ACTIVE/PASSIVE VERY AGGRESSIVE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Active/Passive Very Aggressive Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Active/Passive Very Aggressive Portfolio	$13	0.25%

Portfolio Statistics

Total Net Assets (000's)$97,128
# of Portfolio Holdings (Derivatives not included, if applicable)22
Portfolio Turnover Rate29%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
iShares Core S&P 500 ETF	12.8%
Northwestern Mutual Series Fund, Inc., International Equity Portfolio	9.1%
State Street SPDR Portfolio S&P 400 Mid Cap ETF	7.7%
Northwestern Mutual Series Fund, Inc., Emerging Markets Equity Portfolio	7.0%
iShares Core MSCI EAFE ETF	7.0%
Northwestern Mutual Series Fund, Inc., International Growth Portfolio	5.4%
Northwestern Mutual Series Fund, Inc., Large Cap Blend Portfolio	5.2%
Northwestern Mutual Series Fund, Inc., Focused Appreciation Portfolio	5.2%
Northwestern Mutual Series Fund, Inc., Domestic Equity Portfolio	5.2%
Invesco S&P 500 Equal Weight ETF	5.2%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	3.7%
Commodities	0.6%
Foreign Equity	33.8%
Domestic Equity	61.9%

Additional Information

ACTIVE/PASSIVE VERY AGGRESSIVE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

ACTIVE/PASSIVE CONSERVATIVE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Active/Passive Conservative Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Active/Passive Conservative Portfolio	$14	0.27%

Portfolio Statistics

Total Net Assets (000's)$34,233
# of Portfolio Holdings (Derivatives not included, if applicable)25
Portfolio Turnover Rate20%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
iShares Core U.S. Aggregate Bond ETF	29.2%
Northwestern Mutual Series Fund, Inc., Select Bond Portfolio	24.0%
Northwestern Mutual Series Fund, Inc., Multi-Sector Bond Portfolio	10.5%
State Street SPDR Portfolio Long Term Treasury ETF	4.9%
iShares Core S&P 500 ETF	2.7%
State Street SPDR Portfolio S&P 400 Mid Cap ETF	2.5%
Northwestern Mutual Series Fund, Inc., Short-Term Bond Portfolio	2.5%
Northwestern Mutual Series Fund, Inc., International Equity Portfolio	2.5%
Northwestern Mutual Series Fund, Inc., Emerging Markets Equity Portfolio	1.6%
State Street SPDR Dow Jones REIT ETF	1.5%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	3.5%
Commodities	0.4%
Foreign Equity	8.2%
Domestic Equity	16.7%
Fixed Income	71.2%

Additional Information

ACTIVE/PASSIVE CONSERVATIVE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

ACTIVE/PASSIVE MODERATE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Active/Passive Moderate Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Active/Passive Moderate Portfolio	$7	0.14%

Portfolio Statistics

Total Net Assets (000's)$319,768
# of Portfolio Holdings (Derivatives not included, if applicable)27
Portfolio Turnover Rate8%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Northwestern Mutual Series Fund, Inc., Select Bond Portfolio	17.9%
iShares Core S&P 500 ETF	9.3%
iShares Core U.S. Aggregate Bond ETF	6.7%
Northwestern Mutual Series Fund, Inc., International Equity Portfolio	6.2%
Northwestern Mutual Series Fund, Inc., Multi-Sector Bond Portfolio	5.0%
State Street SPDR Portfolio S&P 400 Mid Cap ETF	4.6%
Northwestern Mutual Series Fund, Inc., Large Cap Blend Portfolio	3.8%
Northwestern Mutual Series Fund, Inc., Domestic Equity Portfolio	3.8%
Invesco S&P 500 Equal Weight ETF	3.7%
Northwestern Mutual Series Fund, Inc., Focused Appreciation Portfolio	3.7%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	3.9%
Commodities	0.5%
Foreign Equity	19.8%
Fixed Income	32.4%
Domestic Equity	43.4%

Additional Information

ACTIVE/PASSIVE MODERATE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

ACTIVE/PASSIVE BALANCED PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Active/Passive Balanced Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Active/Passive Balanced Portfolio	$6	0.11%

Portfolio Statistics

Total Net Assets (000's)$2,023,029
# of Portfolio Holdings (Derivatives not included, if applicable)27
Portfolio Turnover Rate5%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Northwestern Mutual Series Fund, Inc., Select Bond Portfolio	24.9%
iShares Core U.S. Aggregate Bond ETF	13.1%
Northwestern Mutual Series Fund, Inc., Multi-Sector Bond Portfolio	7.5%
iShares Core S&P 500 ETF	5.1%
State Street SPDR Portfolio Long Term Treasury ETF	4.8%
Northwestern Mutual Series Fund, Inc., International Equity Portfolio	4.1%
State Street SPDR Portfolio S&P 400 Mid Cap ETF	3.3%
Northwestern Mutual Series Fund, Inc., Emerging Markets Equity Portfolio	3.2%
State Street SPDR Portfolio S&P 600 Small Cap ETF	3.1%
Northwestern Mutual Series Fund, Inc., International Growth Portfolio	2.6%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	3.5%
Commodities	0.5%
Foreign Equity	14.1%
Domestic Equity	30.1%
Fixed Income	51.8%

Additional Information

ACTIVE/PASSIVE BALANCED PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

DOMESTIC EQUITY PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Domestic Equity Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Domestic Equity Portfolio	$26	0.49%

Portfolio Statistics

Total Net Assets (000's)$1,260,830
# of Portfolio Holdings (Derivatives not included, if applicable)67
Portfolio Turnover Rate28%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Apple, Inc.	6.3%
Microsoft Corp.	5.7%
Citigroup, Inc.	3.9%
Amazon.com, Inc.	3.8%
Cisco Systems, Inc.	2.8%
AbbVie, Inc.	2.6%
Exxon Mobil Corp.	2.6%
Philip Morris International, Inc.	2.4%
The Coca-Cola Co.	2.3%
Advanced Micro Devices, Inc.	2.2%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	1.0%
Communication Services	0.9%
Real Estate	1.9%
Utilities	3.8%
Materials	5.2%
Energy	5.8%
Consumer Staples	8.4%
Consumer Discretionary	8.6%
Industrials	11.7%
Health Care	14.4%
Financials	18.2%
Information Technology	20.1%

Additional Information

DOMESTIC EQUITY PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

EMERGING MARKETS EQUITY PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Emerging Markets Equity Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Emerging Markets Equity Portfolio	$44	0.77%

Portfolio Statistics

Total Net Assets (000's)$1,543,063
# of Portfolio Holdings (Derivatives not included, if applicable)71
Portfolio Turnover Rate29%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Samsung Electronics Co., Ltd., Various	10.3%
Taiwan Semiconductor Manufacturing Co., Ltd.	9.9%
SK Hynix, Inc.	8.7%
MediaTek, Inc.	4.4%
Tencent Holdings, Ltd.	4.2%
Grupo Mexico SAB de CV	3.2%
HDFC Bank, Ltd.	3.1%
NAURA Technology Group Co., Ltd. - Class A	2.9%
Contemporary Amperex Technology Co., Ltd. - Class A	2.4%
Chroma ATE, Inc.	2.4%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	1.1%
Real Estate	1.8%
Utilities	1.9%
Energy	2.1%
Consumer Staples	2.3%
Health Care	2.3%
Materials	4.5%
Consumer Discretionary	4.8%
Communication Services	6.8%
Industrials	10.1%
Financials	16.6%
Information Technology	45.7%

Investments by Country of Risk (% of net assets)

Table Summary
Value	Value
Other	22.1%
India	10.4%
China	19.1%
Taiwan	22.5%
South Korea	24.8%

Additional Information

EMERGING MARKETS EQUITY PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

EQUITY INCOME PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Equity Income Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Equity Income Portfolio	$30	0.57%

Portfolio Statistics

Total Net Assets (000's)$826,555
# of Portfolio Holdings (Derivatives not included, if applicable)117
Portfolio Turnover Rate22%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Amazon.com, Inc.	5.4%
Microsoft Corp.	4.3%
Apple, Inc.	3.8%
The Southern Co., Various	2.2%
MetLife, Inc.	2.0%
Intel Corp.	2.0%
Citigroup, Inc.	1.8%
QUALCOMM, Inc.	1.8%
JPMorgan Chase & Co.	1.7%
TotalEnergies SE, Various	1.7%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	0.3%
Communication Services	2.6%
Materials	3.0%
Real Estate	3.0%
Utilities	5.7%
Consumer Staples	6.6%
Consumer Discretionary	7.4%
Energy	8.4%
Health Care	13.0%
Industrials	13.8%
Information Technology	16.7%
Financials	19.5%

Additional Information

EQUITY INCOME PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

FOCUSED APPRECIATION PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Focused Appreciation Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Focused Appreciation Portfolio	$29	0.60%

Portfolio Statistics

Total Net Assets (000's)$1,434,485
# of Portfolio Holdings (Derivatives not included, if applicable)34
Portfolio Turnover Rate2%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
NVIDIA Corp.	12.6%
Alphabet, Inc., Various	10.6%
Tesla, Inc.	8.4%
Meta Platforms, Inc. - Class A	6.4%
Amazon.com, Inc.	5.9%
Visa, Inc. - Class A	4.9%
The Boeing Co.	4.8%
Microsoft Corp.	4.5%
Netflix, Inc.	4.2%
Monster Beverage Corp.	3.7%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	2.2%
Consumer Staples	3.8%
Financials	7.4%
Industrials	7.5%
Health Care	11.5%
Consumer Discretionary	17.3%
Communication Services	23.3%
Information Technology	27.0%

Additional Information

FOCUSED APPRECIATION PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

GOVERNMENT MONEY MARKET PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Government Money Market Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Government Money Market Portfolio	$17	0.34%

Portfolio Statistics

Total Net Assets (000's)$482,500
# of Portfolio Holdings (Derivatives not included, if applicable)168

What did the Portfolio invest in? (Derivatives not included, if applicable)

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	-1.0%
Repurchase Agreements	37.7%
US Government & Agencies	63.3%

Additional Information

GOVERNMENT MONEY MARKET PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

GROWTH STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Growth Stock Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Growth Stock Portfolio	$21	0.42%

Portfolio Statistics

Total Net Assets (000's)$1,455,300
# of Portfolio Holdings (Derivatives not included, if applicable)61
Portfolio Turnover Rate14%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
NVIDIA Corp.	17.3%
Alphabet, Inc., Various	8.4%
Broadcom, Inc.	5.2%
Microsoft Corp.	5.0%
Apple, Inc.	4.8%
Meta Platforms, Inc. - Class A	4.3%
Samsung Electronics Co., Ltd., GDR	4.2%
Amazon.com, Inc.	3.9%
Eli Lilly & Co.	3.3%
Carvana Co.	3.2%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	0.6%
Materials	0.4%
Utilities	0.4%
Industrials	5.1%
Health Care	6.0%
Financials	7.2%
Consumer Discretionary	12.5%
Communication Services	15.1%
Information Technology	52.7%

Additional Information

GROWTH STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

HIGH YIELD BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the High Yield Bond Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
High Yield Bond Portfolio	$23	0.45%

Portfolio Statistics

Total Net Assets (000's)$710,571
# of Portfolio Holdings (Derivatives not included, if applicable)509
Portfolio Turnover Rate17%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
CCO Holdings LLC / CCO Holdings Capital Corp., Various	2.0%
TransDigm, Inc., Various	1.7%
HUB International, Ltd., Various	1.6%
Venture Global Plaquemines LNG LLC, Various	1.2%
Cloud Software Group, Inc., Various	1.2%
NRG Energy, Inc., Various	1.1%
Ford Motor Credit Co. LLC, Various	1.1%
Ardonagh Group Finance, Ltd., 8.875%, 2/15/32	1.0%
1011778 BC ULC / New Red Finance, Inc., Various	1.0%
Antero Midstream Partners LP / Antero Midstream Finance Corp., Various	1.0%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	3.5%
Communication Services	0.0%
Diversified	0.3%
Utilities	2.7%
Basic Materials	4.1%
Energy	10.8%
Technology	11.1%
Industrial	11.4%
Communications	11.7%
Financial	11.9%
Consumer, Non-Cyclical	15.1%
Consumer, Cyclical	17.4%

Additional Information

HIGH YIELD BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

INDEX 400 STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Index 400 Stock Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Index 400 Stock Portfolio	$13	0.24%

Portfolio Statistics

Total Net Assets (000's)$1,703,294
# of Portfolio Holdings (Derivatives not included, if applicable)402
Portfolio Turnover Rate8%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Twilio, Inc.	0.9%
Carpenter Technology Corp.	0.8%
MKS, Inc.	0.8%
Curtiss-Wright Corp.	0.8%
Entegris, Inc.	0.7%
nVent Electric PLC	0.7%
ATI, Inc.	0.7%
Illumina, Inc.	0.7%
TechnipFMC PLC	0.7%
Sterling Infrastructure, Inc.	0.7%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	0.8%
Communication Services	1.5%
Utilities	3.0%
Consumer Staples	3.1%
Energy	4.3%
Materials	6.3%
Real Estate	6.6%
Health Care	8.6%
Consumer Discretionary	10.5%
Financials	14.6%
Information Technology	15.3%
Industrials	25.4%

Additional Information

INDEX 400 STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

INDEX 500 STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Index 500 Stock Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Index 500 Stock Portfolio	$10	0.19%

Portfolio Statistics

Total Net Assets (000's)$8,146,936
# of Portfolio Holdings (Derivatives not included, if applicable)504
Portfolio Turnover Rate1%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
NVIDIA Corp.	7.5%
Apple, Inc.	6.6%
Alphabet, Inc., Various	5.8%
Microsoft Corp.	4.3%
Amazon.com, Inc.	3.6%
Broadcom, Inc.	2.8%
Micron Technology, Inc.	2.0%
Meta Platforms, Inc. - Class A	1.9%
Tesla, Inc.	1.8%
Eli Lilly & Co.	1.5%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	0.5%
Real Estate	1.8%
Materials	1.8%
Utilities	2.2%
Energy	3.0%
Consumer Staples	4.5%
Health Care	8.9%
Industrials	8.9%
Consumer Discretionary	9.3%
Communication Services	9.6%
Financials	11.7%
Information Technology	37.8%

Additional Information

INDEX 500 STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

INDEX 600 STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Index 600 Stock Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Index 600 Stock Portfolio	$14	0.26%

Portfolio Statistics

Total Net Assets (000's)$618,483
# of Portfolio Holdings (Derivatives not included, if applicable)605
Portfolio Turnover Rate14%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
FormFactor, Inc.	0.7%
ViaSat, Inc.	0.7%
Molina Healthcare, Inc.	0.6%
Argan, Inc.	0.6%
BrightSpring Health Services	0.6%
Element Solutions, Inc.	0.6%
MaxLinear, Inc.	0.6%
Krystal Biotech, Inc.	0.5%
ESCO Technologies, Inc.	0.5%
Match Group, Inc.	0.5%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	0.4%
Utilities	2.0%
Consumer Staples	3.3%
Communication Services	3.5%
Materials	4.3%
Energy	4.9%
Real Estate	6.3%
Health Care	12.2%
Consumer Discretionary	13.8%
Information Technology	14.2%
Industrials	17.0%
Financials	18.1%

Additional Information

INDEX 600 STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

INFLATION MANAGED PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Inflation Managed Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Inflation Managed Portfolio	$22	0.45%

Portfolio Statistics

Total Net Assets (000's)$424,305
# of Portfolio Holdings (Derivatives not included, if applicable)206
Portfolio Turnover Rate64%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
US Treasury Inflation Index Bond, Various	50.5%
Federal Home Loan Mortgage Corp., Various	2.2%
Government National Mortgage Association, 5%, 8/20/53	1.2%
Capital One Financial Corp., Various	1.0%
Federal National Mortgage Association, 5.5%, 12/1/55	0.9%
Fastnet Funding Co. LLC	0.9%
Aquitaine Funding Co. LLC	0.9%
Oracle Corp., Various	0.8%
The Goldman Sachs Group, Inc., Various	0.8%
Santander Mortgage Asset Receivables Trust, Series 2026-NQM4, Class A1, 5.49%, 5/25/66	0.6%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	3.1%
Municipal Bonds	0.3%
Corporate Bonds	19.4%
Structured Products	26.6%
Governments	50.6%

Additional Information

INFLATION MANAGED PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

INTERNATIONAL EQUITY PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the International Equity Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
International Equity Portfolio	$35	0.67%

Portfolio Statistics

Total Net Assets (000's)$2,553,628
# of Portfolio Holdings (Derivatives not included, if applicable)88
Portfolio Turnover Rate9%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Taiwan Semiconductor Manufacturing Co., Ltd.	4.8%
BNP Paribas SA	3.6%
Johnson Controls International PLC	3.5%
Infineon Technologies AG	3.0%
SK Hynix, Inc.	2.9%
Banco Santander SA	2.9%
Barclays PLC	2.7%
GSK PLC	2.4%
UBS Group AG	2.4%
Itau Unibanco Holding SA	2.3%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	1.1%
Utilities	0.4%
Real Estate	1.0%
Energy	4.6%
Communication Services	4.6%
Consumer Staples	6.1%
Materials	6.2%
Consumer Discretionary	7.9%
Industrials	11.8%
Health Care	12.8%
Information Technology	16.6%
Financials	26.9%

Investments by Country of Risk (% of net assets)

Table Summary
Value	Value
Other	33.9%
Switzerland	5.1%
South Korea	5.5%
France	7.0%
Japan	7.7%
Germany	9.4%
United Kingdom	12.4%
United States	17.9%

Additional Information

INTERNATIONAL EQUITY PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

INTERNATIONAL GROWTH PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the International Growth Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
International Growth Portfolio	$32	0.61%

Portfolio Statistics

Total Net Assets (000's)$1,249,121
# of Portfolio Holdings (Derivatives not included, if applicable)59
Portfolio Turnover Rate33%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
ASML Holding NV	11.1%
Taiwan Semiconductor Manufacturing Co., Ltd.	5.0%
GE Vernova, Inc.	4.1%
Schneider Electric SE	3.7%
Rolls-Royce Holdings PLC	3.6%
Safran SA	3.2%
Airbus SE	3.1%
Advantest Corp.	3.0%
BAE Systems PLC	2.8%
ABB, Ltd.	2.8%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	1.5%
Consumer Staples	0.9%
Health Care	3.0%
Consumer Discretionary	6.2%
Financials	7.2%
Materials	11.1%
Information Technology	27.9%
Industrials	42.2%

Investments by Country of Risk (% of net assets)

Table Summary
Value	Value
Other	9.0%
Taiwan	5.0%
Switzerland	6.6%
Sweden	9.6%
France	9.9%
United Kingdom	11.8%
Netherlands	12.6%
Japan	15.3%
United States	18.7%

Additional Information

INTERNATIONAL GROWTH PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

LARGE CAP BLEND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Large Cap Blend Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Large Cap Blend Portfolio	$36	0.72%

Portfolio Statistics

Total Net Assets (000's)$176,093
# of Portfolio Holdings (Derivatives not included, if applicable)64
Portfolio Turnover Rate30%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
NVIDIA Corp.	7.9%
Alphabet, Inc. - Class A	6.8%
Apple, Inc.	5.7%
Amazon.com, Inc.	4.6%
Broadcom, Inc.	4.0%
Microsoft Corp.	3.3%
Micron Technology, Inc.	3.2%
Mastercard, Inc. - Class A	2.9%
Wells Fargo & Co.	2.5%
American Express Co.	2.4%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	1.3%
Real Estate	0.7%
Materials	0.8%
Consumer Staples	2.4%
Energy	3.0%
Utilities	4.1%
Industrials	6.8%
Health Care	8.2%
Consumer Discretionary	11.2%
Communication Services	11.6%
Financials	14.8%
Information Technology	35.1%

Additional Information

LARGE CAP BLEND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

LARGE CAP CORE STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Large Cap Core Stock Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Large Cap Core Stock Portfolio	$22	0.43%

Portfolio Statistics

Total Net Assets (000's)$861,383
# of Portfolio Holdings (Derivatives not included, if applicable)150
Portfolio Turnover Rate47%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
NVIDIA Corp.	8.6%
Apple, Inc.	5.3%
Alphabet, Inc. - Class A	5.2%
Amazon.com, Inc.	5.0%
Microsoft Corp.	4.3%
Broadcom, Inc.	3.6%
Micron Technology, Inc.	2.6%
Advanced Micro Devices, Inc.	2.2%
The Goldman Sachs Group, Inc.	1.9%
Berkshire Hathaway, Inc. - Class B	1.9%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	0.2%
Real Estate	0.9%
Materials	1.9%
Utilities	2.8%
Energy	3.9%
Consumer Staples	5.7%
Communication Services	7.8%
Industrials	8.1%
Health Care	9.5%
Consumer Discretionary	11.3%
Financials	11.8%
Information Technology	36.1%

Additional Information

LARGE CAP CORE STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

LARGE COMPANY VALUE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Large Company Value Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Large Company Value Portfolio	$38	0.74%

Portfolio Statistics

Total Net Assets (000's)$179,133
# of Portfolio Holdings (Derivatives not included, if applicable)49
Portfolio Turnover Rate40%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Marsh & McLennan Cos., Inc.	4.0%
Microsoft Corp.	3.7%
Duke Energy Corp.	3.5%
Berkshire Hathaway, Inc. - Class B	3.4%
Johnson & Johnson	3.2%
Amazon.com, Inc.	3.2%
JPMorgan Chase & Co.	3.2%
Becton Dickinson and Co.	3.2%
Enterprise Products Partners LP	2.7%
BlackRock, Inc.	2.7%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	1.8%
Communication Services	1.0%
Consumer Discretionary	4.4%
Utilities	5.1%
Materials	5.3%
Energy	7.9%
Industrials	11.8%
Information Technology	12.1%
Consumer Staples	12.3%
Health Care	16.2%
Financials	22.1%

Additional Information

LARGE COMPANY VALUE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

LONG-TERM U.S. GOVERNMENT BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Long-Term U.S. Government Bond Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Long-Term U.S. Government Bond Portfolio	$122	2.46%

Portfolio Statistics

Total Net Assets (000's)$121,305
# of Portfolio Holdings (Derivatives not included, if applicable)111
Portfolio Turnover Rate3%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
US Treasury Bond, Various	119.5%
Uniform Mortgage Backed Security TBA, Various	9.8%
US Treasury Inflation Index Bond, Various	6.3%
US Treasury Note, Various	4.6%
Federal Home Loan Mortgage Corp., Series 4092, Class AY, 3%, 8/15/32	1.7%
Federal Home Loan Mortgage Corp., Series 4387, Class AZ, 4%, 9/15/44	1.3%
Federal Home Loan Mortgage Corp., 4.5%, 5/1/54	1.2%
Federal Home Loan Mortgage Corp., Series 4398, Class ZX, 4%, 9/15/54	0.7%
US Treasury Bond Strip Coupon, Various	0.6%
Federal National Mortgage Association, Series 2016-61, Class ML, 3%, 9/25/46	0.6%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	-51.6%
Corporate Bonds	0.5%
Structured Products	19.3%
Governments	131.8%

Additional Information

LONG-TERM U.S. GOVERNMENT BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

MID CAP GROWTH STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Mid Cap Growth Stock Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Mid Cap Growth Stock Portfolio	$28	0.54%

Portfolio Statistics

Total Net Assets (000's)$1,109,768
# of Portfolio Holdings (Derivatives not included, if applicable)112
Portfolio Turnover Rate57%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Datadog, Inc. - Class A	3.0%
Snowflake, Inc.	3.0%
Comfort Systems USA, Inc.	2.8%
Astera Labs, Inc.	2.4%
Robinhood Markets, Inc. - Class A	2.2%
Teradyne, Inc.	2.1%
Lumentum Holdings, Inc.	2.1%
Fastenal Co.	2.0%
Rocket Lab Corp.	2.0%
Chipotle Mexican Grill, Inc.	1.9%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	0.7%
Materials	0.5%
Real Estate	0.6%
Utilities	1.2%
Communication Services	1.9%
Consumer Staples	2.4%
Energy	3.3%
Financials	6.7%
Consumer Discretionary	11.3%
Health Care	14.3%
Industrials	23.6%
Information Technology	33.5%

Additional Information

MID CAP GROWTH STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

MID CAP VALUE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Mid Cap Value Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Mid Cap Value Portfolio	$37	0.70%

Portfolio Statistics

Total Net Assets (000's)$709,763
# of Portfolio Holdings (Derivatives not included, if applicable)120
Portfolio Turnover Rate39%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Kimberly-Clark Corp.	2.2%
Commerce Bancshares, Inc.	2.0%
Zimmer Biomet Holdings, Inc.	2.0%
Henry Schein, Inc.	2.0%
Labcorp Holdings, Inc.	1.8%
Evergy, Inc.	1.6%
Packaging Corp. of America	1.6%
Xcel Energy, Inc.	1.6%
Becton Dickinson and Co.	1.6%
Enterprise Products Partners LP	1.6%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	2.9%
Communication Services	0.6%
Consumer Discretionary	4.3%
Materials	4.3%
Consumer Staples	6.0%
Real Estate	6.5%
Energy	7.0%
Information Technology	9.3%
Utilities	9.7%
Health Care	14.9%
Industrials	16.1%
Financials	18.4%

Additional Information

MID CAP VALUE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

MULTI-SECTOR BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Multi-Sector Bond Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Multi-Sector Bond Portfolio	$38	0.75%

Portfolio Statistics

Total Net Assets (000's)$1,402,267
# of Portfolio Holdings (Derivatives not included, if applicable)1,031
Portfolio Turnover Rate20%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Uniform Mortgage Backed Security TBA, Various	9.5%
Citigroup Global Markets, Inc. Repurchase Agreement, 3.69%, 7/1/26	3.5%
US Treasury Bond, Various	3.3%
Canadian Imperial Bank of Commerce Repurchase Agreement, 2.24%, 7/2/26	2.0%
Saudi Government International Bond, Various	1.9%
Republic of South Africa Government International Bond, Various	1.5%
Colombian TES, Various	1.4%
United Mexican States, Various	1.4%
Abu Dhabi Government International Bond, Various	1.3%
Petroleos Mexicanos, Various	1.3%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	-2.5%
Warrants	0.0%
Convertible Corporate Bonds	0.0%
Common Stocks	0.1%
Municipal Bonds	0.1%
Bank Loan Obligations	4.5%
Governments	25.6%
Structured Products	33.5%
Corporate Bonds	38.7%

Additional Information

MULTI-SECTOR BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

RESEARCH INTERNATIONAL CORE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Research International Core Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Research International Core Portfolio	$34	0.65%

Portfolio Statistics

Total Net Assets (000's)$1,061,065
# of Portfolio Holdings (Derivatives not included, if applicable)116
Portfolio Turnover Rate13%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Mizuho Financial Group, Inc.	3.0%
Schneider Electric SE	2.8%
Tokyo Electron, Ltd.	2.7%
ASML Holding NV	2.7%
Taiwan Semiconductor Manufacturing Co., Ltd.	2.2%
Novartis AG	2.1%
Hitachi, Ltd.	2.1%
TotalEnergies SE	1.9%
AstraZeneca PLC	1.8%
Linde PLC	1.8%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	1.9%
Utilities	2.6%
Communication Services	3.5%
Energy	4.1%
Consumer Staples	5.0%
Consumer Discretionary	7.2%
Materials	8.1%
Health Care	10.5%
Information Technology	13.4%
Industrials	17.2%
Financials	26.5%

Investments by Country of Risk (% of net assets)

Table Summary
Value	Value
Other	28.2%
Germany	5.3%
Netherlands	5.8%
France	8.4%
United Kingdom	12.7%
United States	14.2%
Japan	23.5%

Additional Information

RESEARCH INTERNATIONAL CORE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

SELECT BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Select Bond Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Select Bond Portfolio	$15	0.31%

Portfolio Statistics

Total Net Assets (000's)$2,881,962
# of Portfolio Holdings (Derivatives not included, if applicable)956
Portfolio Turnover Rate145%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
US Treasury Note, Various	18.3%
Federal National Mortgage Association, Various	13.8%
US Treasury Bond, Various	11.2%
Federal Home Loan Mortgage Corp., Various	7.7%
Government National Mortgage Association, Various	5.0%
The Goldman Sachs Group, Inc., Various	1.5%
Uniform Mortgage Backed Security TBA, Various	1.3%
Morgan Stanley, Various	1.1%
Honeywell Aerospace, Inc., Various	0.7%
Government National Mortgage Association, Series 2025-1, Class GC, 3.5%, 10/20/51	0.7%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	-1.4%
Municipal Bonds	0.1%
Corporate Bonds	27.4%
Governments	30.2%
Structured Products	43.7%

Additional Information

SELECT BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

SHORT-TERM BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Short-Term Bond Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Short-Term Bond Portfolio	$20	0.40%

Portfolio Statistics

Total Net Assets (000's)$401,024
# of Portfolio Holdings (Derivatives not included, if applicable)910
Portfolio Turnover Rate65%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
US Treasury Note, Various	22.5%
Federal National Mortgage Association, Various	3.4%
Federal Home Loan Mortgage Corp., Various	2.4%
Keurig Dr. Pepper, Inc., Various	0.9%
Volkswagen Group of America Finance LLC, Various	0.7%
The Goldman Sachs Group, Inc., Various	0.7%
HCA, Inc., Various	0.7%
SBA Tower Trust, Various	0.6%
Crown Castle, Inc., Various	0.6%
Hyundai Capital America, Various	0.6%

Asset Type Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	3.1%
Governments	23.1%
Structured Products	34.6%
Corporate Bonds	39.2%

Additional Information

SHORT-TERM BOND PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

SMALL CAP GROWTH STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Small Cap Growth Stock Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Small Cap Growth Stock Portfolio	$31	0.55%

Portfolio Statistics

Total Net Assets (000's)$899,076
# of Portfolio Holdings (Derivatives not included, if applicable)186
Portfolio Turnover Rate54%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
FirstCash Holdings, Inc.	1.3%
Moog, Inc. - Class A	1.2%
MKS, Inc.	1.1%
Marex Group PLC	1.1%
Dave, Inc. - Class A	1.0%
Dorman Products, Inc.	1.0%
Alignment Healthcare, Inc.	1.0%
Ensign Group, Inc.	1.0%
Casella Waste Systems, Inc. - Class A	1.0%
MYR Group, Inc.	1.0%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	0.3%
Investment Companies	0.3%
Utilities	0.6%
Communication Services	1.4%
Real Estate	1.5%
Consumer Staples	3.1%
Energy	3.5%
Materials	3.6%
Consumer Discretionary	7.9%
Financials	8.2%
Industrials	19.9%
Information Technology	21.2%
Health Care	28.5%

Additional Information

SMALL CAP GROWTH STOCK PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

SMALL CAP VALUE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

This semi-annual shareholder report contains important information about the Small Cap Value Portfolio (the "Portfolio"), a series of the Northwestern Mutual Series Fund, Inc., for the period of 1/1/2026 to 6/30/2026. You can find additional information about the Portfolio at www.nmseriesfund.com. You can also request this information by contacting us at 1-888-455-2232 or by email at vavldocrequest@northwesternmutual.com.

What were the Portfolio's costs for the past six months?

(based on a hypothetical $10,000 investment)

Table Summary
Portfolio Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
Small Cap Value Portfolio	$48	0.86%

Portfolio Statistics

Total Net Assets (000's)$656,351
# of Portfolio Holdings (Derivatives not included, if applicable)208
Portfolio Turnover Rate30%

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Table Summary
Pinnacle Financial Partners, Inc.	2.4%
Columbia Banking System, Inc.	1.8%
Curbline Properties Corp.	1.5%
PennyMac Financial Services, Inc.	1.2%
CareTrust REIT, Inc.	1.2%
Hut 8 Corp.	1.2%
Cytokinetics, Inc.	1.1%
Vishay Intertechnology, Inc.	1.0%
HA Sustainable Infrastructure Capital, Inc.	1.0%
Arcosa, Inc.	1.0%

Sector Weightings (% of net assets)

Table Summary
Value	Value
Short-Term Investments & Other Net Assets	2.7%
Consumer Staples	1.9%
Communication Services	2.4%
Materials	4.9%
Utilities	5.2%
Energy	6.7%
Information Technology	7.1%
Real Estate	8.8%
Consumer Discretionary	10.1%
Health Care	10.9%
Industrials	13.1%
Financials	26.2%

Additional Information

SMALL CAP VALUE PORTFOLIO

Northwestern Mutual Series Fund, Inc.

June 30, 2026

Semi-Annual Shareholder Report

Washington, D.C. 20549

CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT INVESTMENT COMPANIES

REPORT ON FORM N-CSR

Item 1. Reports to Stockholders.

ACTIVE/PASSIVE AGGRESSIVE PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Asset Type Weightings (% of net assets)

Additional Information

ACTIVE/PASSIVE AGGRESSIVE PORTFOLIO

ACTIVE/PASSIVE VERY AGGRESSIVE PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Asset Type Weightings (% of net assets)

Additional Information

ACTIVE/PASSIVE VERY AGGRESSIVE PORTFOLIO

ACTIVE/PASSIVE CONSERVATIVE PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Asset Type Weightings (% of net assets)

Additional Information

ACTIVE/PASSIVE CONSERVATIVE PORTFOLIO

ACTIVE/PASSIVE MODERATE PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Asset Type Weightings (% of net assets)

Additional Information

ACTIVE/PASSIVE MODERATE PORTFOLIO

ACTIVE/PASSIVE BALANCED PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Asset Type Weightings (% of net assets)

Additional Information

ACTIVE/PASSIVE BALANCED PORTFOLIO

DOMESTIC EQUITY PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Sector Weightings (% of net assets)

Additional Information

DOMESTIC EQUITY PORTFOLIO

EMERGING MARKETS EQUITY PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Sector Weightings (% of net assets)

Investments by Country of Risk (% of net assets)

Additional Information

EMERGING MARKETS EQUITY PORTFOLIO

EQUITY INCOME PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Sector Weightings (% of net assets)

Additional Information

EQUITY INCOME PORTFOLIO

FOCUSED APPRECIATION PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)

Top Ten Holdings (% of net assets)

Sector Weightings (% of net assets)

Additional Information

FOCUSED APPRECIATION PORTFOLIO

What were the Portfolio's costs for the past six months?

Portfolio Statistics

What did the Portfolio invest in? (Derivatives not included, if applicable)