Exhibit 99.1

GERDAU S.A.

Condensed consolidated interim financial statements

as of June 30, 2025

GERDAU S.A.

CONSOLIDATED BALANCE SHEETS

In thousands of Brazilian reais (R$)

(Unaudited)

The accompanying notes are an integral part of these Condensed Consolidated Interim Financial Statements

GERDAU S.A.

CONSOLIDATED BALANCE SHEETS

In thousands of Brazilian reais (R$)

(Unaudited)

The accompanying notes are an integral part of these Condensed Consolidated Interim Financial Statements

GERDAU S.A.

CONSOLIDATED STATEMENTS OF INCOME

In thousands of Brazilian reais (R$)

(Unaudited)

The accompanying notes are an integral part of these Condensed Consolidated Interim Financial Statements

GERDAU S.A.

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME

In thousands of Brazilian reais (R$)

(Unaudited)

The accompanying notes are an integral part of these Condensed Consolidated Interim Financial Statements

GERDAU S.A.

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY

in thousands of Brazilian reais (R$)

(Unaudited)

The accompanying notes are an integral part of these Condensed Consolidated Interim Financial Statements

GERDAU S.A.

CONSOLIDATED STATEMENTS OF CASH FLOWS

In thousands of Brazilian reais (R$)

(Unaudited)  

The accompanying notes are an integral part of these Condensed Consolidated Interim Financial Statements

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

NOTE 1 - GENERAL INFORMATION

Gerdau S.A. is a publicly traded corporation (sociedade anônima) with its corporate domicile in the city of São Paulo, Brazil. Gerdau S.A and subsidiaries (collectively referred to as the “Company”) is a leading producer of long steel in the Americas and one of the largest suppliers of special steel in the world. In Brazil, the Company also produces flat steel and iron ore, activities which expanded the product mix and made its operations even more competitive. The Company believes it is the largest recycler in Latin America and around the world it transforms each year millions of tons of scrap into steel, reinforcing its commitment to sustainable development of the regions where it operates. Gerdau is listed on the São Paulo and New York stock exchanges.

The Condensed Consolidated Interim Financial Statements of the Company were approved by the Management on July 31, 2025.

NOTE 2 - SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES

2.1 - Basis of Presentation

The Company's Condensed Consolidated Interim Financial Statements for the three-month and six-month period ended on June 30, 2025 have been prepared in accordance with International Accounting Standard (IAS) Nº 34, which establishes the content of condensed interim financial statements. These Condensed Consolidated Interim Financial Statements should be read in conjunction with the Consolidated Financial Statements of Gerdau S.A., as of December 31, 2024, which were prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the International Accounting Standards Board - IASB.

The preparation of the Condensed Consolidated Interim Financial Statements in accordance with IAS 34 requires Management to make accounting estimates. The Condensed Consolidated Interim Financial Statements have been prepared using the historical cost as its basis, except for the valuation of certain financial instruments, which are measured at fair value.

The accounting policies applied in this Condensed Consolidated Interim Financial Statements are the same as those applied in the Consolidated Financial Statements for the year ended December 31, 2024.

Starting with the disclosure of the results of 2025, the Company began to disclose the information and results of its business segments as follows:

· Brazil Segment: includes the long, flat and special steel operations and the iron ore operation located in Brazil and and joint ventures (note 3.2) and associates (note 3.3) companies located in Brazil.

· North America Segment: includes the long and specialty steel operations located in Canada and the United States and the joint ventures (note 3.2) located in Canada and Mexico;

· South America Segment: includes the operations in Argentina, Peru and Uruguay.

With these changes, the information and results of the former Special Steel Segment, which included the special steel operations located in Brazil and the United States, will now be disclosed jointly with the other segments, according to their geographic location, as the Brazil Segment and the North America Segment, respectively.

This new format for disclosing information and results is in line with recent changes in the global steel industry scenario, which have led to an increasing regionalization of markets, business dynamics and local currencies of these operations, improving the presentation of Gerdau's results in Brazil and North America, the main regions in which it operates. The comparative information of the segments presented in this Interim Information has been adjusted to reflect this new composition.

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

2.2 – New accounting standards

The issued and/or reviewed IFRS standards made by the IASB that are effective for the year started in 2025 had no impact on the Company's Financial Statements. In addition, the IASB issued/reviewed some IFRS standards, which have mandatory adoption for the year 2026 and/or after, and the Company is assessing the adoption impact of these standards in its Consolidated Financial Statements.

- Issuance of IFRS 18 – Presentation and Disclosure in Financial Statements. It will replace IAS 1 – Presentation of Financial Statements, introducing new requirements that will help achieve comparability of the financial performance of similar entities and provide more relevant information and transparency to users. Although IFRS 18 does not impact the recognition or measurement of items in financial statements, its impacts on presentation and disclosure are expected to be widespread, in particular those related to the demonstration of financial performance and the provision of performance measures defined by management within the financial statements. This standard is effective for years beginning on/or after January 1, 2027. The Company is evaluating the impacts on its Financial Statements of adopting this standard.

- Issuance of IFRS 19 – Subsidiaries without Public Accountability: Disclosures. Establishes simplified disclosures requirements for consolidated or individual financial statements of entities eligible for the application of this standard. These rules are effective for fiscal years beginning on/or after January 1, 2027. The Company does not expect material impacts on its Financial Statements.

- Amendment to IFRS 9 and IFRS 7 – Amendments to the classification and measurement of financial instruments. It clarifies aspects related to the classification and measurement of financial instruments. This amendment to the standards is effective for years beginning on/or after January 1, 2026. The Company is evaluating the impacts on its Financial Statements of adopting these standards.

- Amendment to IFRS 9 and IFRS 7 – Contracts that refer to electricity dependent on nature. Clarifies aspects related to the application and disclosure of purchase and sale contracts exposed to variations in electricity generation dependent on uncontrollable natural conditions and related financial instruments. This amendment to the standards is effective for fiscal years beginning on or after January 1, 2026. The Company does not expect significant impacts on its Financial Statements.

- Annual improvements to IFRS Accounting Standards. It applies amendments to IFRS 1, addressing first-adoption aspects related to hedge accounting; IFRS 7, covering aspects of gain and loss on the reversal of a financial instrument, credit risk disclosures, and the difference between fair value and transaction price; IFRS 9, addressing aspects related to the reversal of leasing liabilities and transaction price; IFRS 10, addressing the determination of the “de facto agent” and IAS 7, addressing aspects related to the cost method. These amendments are effective for years beginning on/or after January 1, 2026. The Company does not expect material impacts on its Financial Statements.

2.3 - Increased tariffs on exports to the United States

Following the announcement by the United States government of an increase in tariffs on exports of products from Brazil, the Company has been monitoring, carefully, the potential effects that the U.S. tariffs on Brazil could have on the domestic market, such as a ripple effect on the consumption of steel in Brazil.

NOTE 3 – CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

3.1 - Subsidiaries

The Company did not have material changes of interest in subsidiaries for the period ended on June 30, 2025, when compared to those existing on December 31, 2024, except in relation to the acquisition of control of Gerdau Summit Aços Fundidos e Forjados S.A., Rio do Sangue Energia S.A., Comercial Gerdau Aços Planos Ltda. e Paranatinga Energia S.A., described in Note 3.4.

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

3.2 - Joint Ventures

Listed below are the interests in joint ventures:

(*) The voting capital is substantially equal to the total capital. The interests reported represent the ownership percentage held directly and indirectly held in the joint venture.

Although the Company owns more than 50% of Gerdau Corsa S.A.P.I. de C.V., it does not consolidate the financial statements of this joint venture entity, due to joint control agreements with the other shareholders that prevent the Company from controlling the decisions in conducting the joint venture’s business. The Company owns 1.32% of MRS Logística S.A. and due to the existence of a shareholders' agreement, a joint venture business and the existence of significant influence provided for in the accounting standard for the application of the equity method is characterized.

The Company presents the joint venture information in aggregate, since the investments in these entities are not individually material. The financial information of these joint ventures, accounted for under the equity method, is shown below:

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

3.3 — Associate companies

Listed below is the interest in associate companies:

(*) The voting capital is substantially equal to the total capital. The interests reported represent the ownership percentage held directly and indirectly.

The Company does not consolidate the Financial Statements of Dona Francisca Energética S.A. despite holding more than 50% of the total capital of this affiliate, due to protection rights granted to other shareholders that prevent the Company from fully implementing decisions regarding the conduct of the affiliate’s business.

The summarized financial information of the associate companies, accounted for under the equity method, is shown as follows:

3.4 — Acquisition of company control

a) Gerdau Summit Aços Fundidos e Forjados S.A. (Gerdau Summit)

On February 10, 2025, the Company, after fulfilling all the conditions precedent, including approval by the antitrust authorities, concluded the transaction with Sumitomo Corporation and The Japan Steel Works Ltd., for the acquisition of 39.53% and 1.74%, respectively, of the total shares issued by Gerdau Summit Aços Fundidos e Forjados S.A. (“Gerdau Summit”). With the closing of the transaction, the Company owns 100% of the Gerdau Summit’s capital. The acquisition price, paid in cash with own resources, was approximately US$ 32.6 million (equivalent to R$ 188.6 million on the date of completion of the transaction), and as a result of the acquisition, the Company obtained a gain from a bargain purchase of R$ 37.7 million, due to the acquisition price being lower than the fair value of Gerdau Summit, with the gain being recognized in the income statement of the period. Gerdau Summit is located in Pindamonhangaba, in the state of São Paulo, and produces cast and forged steel, especially for the production of cylinders and axles in the steel, aluminum, sugar and ethanol and energy sectors. The transaction is in line with the Company’s strategy of generating greater synergy between its businesses and offering higher value- added products and services to its customers. Gerdau Summit, until then a joint venture, with this transaction becomes a subsidiary of the Company.

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

On May 30, 2025, at the Extraordinary General Meeting, it was decided to incorporate Gerdau Summit into Gerdau S.A., without a capital increase and without the issuance of new shares by the Company, with effect from May 31, 2025.

The Company assessed the fair value of Gerdau Summit's assets and liabilities and the following table summarizes the fair value of assets and liabilities on the date of acquisition of control of the company:

The amounts recognized as net revenue and net income for the six-month period ended June 30, 2025, presented in the Income Statement, attributable to Gerdau Summit, total R$ 322.7 million and R$21.1 million, respectively.

b) Rio do Sangue Energia S.A.

On March 21, 2025, the Company completed the acquisition, from Atiaia Energia S.A., of all the shares of Rio do Sangue Energia S.A., owner of the Small Hydroelectric Power Plant (“PCH”) called Garganta da Jararaca, for R$ 244.5 million. The acquisition price was paid in cash on the closing date with its own available resources. The PCH is located in the state of Mato Grosso and will supply renewable energy to Gerdau's steel production units in Brazil, on a self-generation basis. The acquisition of these assets is in line with the Company's strategy of increasing the cost competitiveness of its business by increasing the self-production of clean energy, and in line with the previously announced decarbonization process. The amounts recognized as revenue and net income for the year attributable to Rio do Sangue Energia S.A., included in the Company's Consolidated Financial Statements since the acquisition date, are not material. Additionally, the revenues and net profit that would be generated by Rio do Sangue Energia S.A. for the six-month period ended June 30, 2025, if control had been obtained at the beginning of the year, would also not be significant.

c) Comercial Gerdau Aços Planos Ltda.

On April 11, 2025, the Company acquired 100% of the capital of Kloeckner Metals Brasil Ltda. from Klöeckner & Co.SE, for approximately R$ 42.9 million. As a result of the acquisition, the Company realized a gain on a bargain purchase of R$ 3.6 million, since the acquisition price was lower than the fair value of the acquired company, and the gain was recognized in the income statement for the period. The acquisition price was paid in cash with available equity. Following the acquisition, the Company changed the name of its new subsidiary to Comercial Gerdau Aços Planos Ltda.. The acquired company's business purpose is the sale of steel products and metal cutting and bending, among other activities. The amounts recognized as revenue and net income for the year, attributable to Comercial Gerdau Aços Planos Ltda., included in the Company's Consolidated Financial Statements since the acquisition date, are not material. Additionally, the revenues and net profit that would have been generated by Comercial Gerdau Aços Planos Ltda. for the six-month period ended June 30, 2025, if control had been obtained at the beginning of the year, would also not have been significant.

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

d) Paranatinga Energia S.A.

On April 28, 2025, the Company, together with Atiaia Energia S.A., completed the acquisition of all the shares of Paranatinga Energia S.A., owner of the Small Hydroelectric Power Plant (PCH) called Paranatinga II, for approximately R$197.2 million, net of consolidated cash of R$ 32.8 million. The acquisition price was paid in cash with its own available resources. This SHP is located in the state of Mato Grosso and will supply renewable energy to Gerdau's steel production units in Brazil, on a self-production basis. The acquisition of this asset is in line with Gerdau's strategy of increasing the cost competitiveness of its business by increasing the self-production of clean energy, and in line with the decarbonization process already announced by the Company. The amounts recognized as revenue and net income for the year, attributable to Paranatinga Energia S.A., included in the Company's Consolidated Financial Statements since the acquisition date, are not material. Additionally, the revenues and net profit that would be generated by Paranatinga Energia S.A. for the six-month period ended June 30, 2025, if control had been obtained at the beginning of the year, would also not be significant.

NOTE 4 – CASH AND CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS

Cash and cash equivalents

Immediately available investments include investments with maturity of up to 90 days or readily redeemable, that means, those that have immediate liquidity and low risk of fair value variation.

Short-term investments

Short-term investments include securities held for immediate trading or available for future sale and substantially include amounts in investment funds, whose portfolio is composed of Bank Deposit Certificates, government bonds, financial bills and debentures, among others, which are used to manage the cash from the Company’s operating activities and recorded at fair value. Income generated by these investments is recorded as financial income.

NOTE 5 – ACCOUNTS RECEIVABLE

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

Accounts receivable by aging are as follows:

NOTE 6 - INVENTORIES

The allowance for adjustment to net realizable value of inventories, on which the provision and reversal of provision are registered with impact on cost of sales, is as follows:

NOTE 7 – INCOME AND SOCIAL CONTRIBUTION TAXES

In Brazil, income taxes include federal income tax (IR) and social contribution (CS), which represents an additional federal income tax. The statutory rates for income tax and social contribution are 25% and 9%, respectively, and are applicable for the periods ended on June 30, 2025 and 2024. The foreign subsidiaries of the Company are subject to taxation at rates ranging between 23% and 35%. The differences between the Brazilian tax rates and the rates of other countries are presented under “Difference in tax rates in foreign companies” in the reconciliation of income tax and social contribution below.

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

a) Reconciliations of income and social contribution taxes at statutory rates to amounts presented in the Statement of Income are as follows:

b) Tax assets not recognized:

The Company did not recognize a portion of tax assets regarding tax losses and negative social contribution from some operations in Brazil in the amount of R$ 312,292 (R$ 300,763 on December 31, 2024), which do not have an expiration date. The subsidiaries abroad had R$ 794,210 (R$ 849,200 as of December 31, 2024) of tax credits on capital losses for which deferred tax assets have not been recognized and which expire between 2029 and 2035 and also several tax losses of state credits in the amount of R$ 272,757 (R$ 326,966 as of December 31, 2024), which expire at various dates between 2031 and 2038.

GERDAU S.A.

NOTES TO THE CONDENSED CONSOLIDATED INTERIM FINANCIAL STATEMENTS

as of June 30, 2025

(In thousands of Brazilian Reais – R$, unless otherwise stated)

(Unaudited)

NOTE 8 – INVESTMENTS