Exhibit 99.1

www.smurfitwestrock.com

Smurfit Westrock Reports Third Quarter 2026 Results

October 28, 2026 – Smurfit Westrock plc (NYSE: SW) today announced the financial results for the third quarter ended September 30, 2026.

Key Points:

Smurfit Westrock plc’s performance for the three months ended September 30, 2026 and 2025 (in millions, except margins and per share data):

Tony Smurfit, President and CEO, commented:

“Set against unprecedented cost inflation and somewhat weaker than anticipated converting volumes, our third quarter performance of Adjusted EBITDA¹ of $1,205 million with an Adjusted EBITDA Margin¹ of 14.8% represents a resilient performance. Across all our regions we continue to make good progress in implementing our owner operator model and developing our innovative packaging approach for our customers. We have also implemented significant pricing initiatives across most paper grades and we expect these should more than offset input costs as these increases are passed through.

“Our North American business continues to make good progress. The region reported Adjusted EBITDA of $760 million and an Adjusted EBITDA margin of 15.6% for the third quarter. We remain sold out in all containerboard grades, and most consumer grades, and our converting businesses in both business areas continue to improve. Our focus on quality and service, as well as investment in productivity and efficiency, is winning customers and has established a strong foundation for future performance. In both Corrugated and Consumer, we continue to see a reduction in loss makers and are optimizing our businesses to improve returns. Most importantly, I am particularly impressed with the expertise and commitment of our people that are leading the change towards a customer centric, performance-led culture.

“Our EMEA & APAC business continues to outperform in a market that is heavily impacted by rising energy costs. The region reported Adjusted EBITDA of $379 million and an Adjusted EBITDA margin of 13.4% for the third quarter. Containerboard price increases to offset costs have been implemented and are being passed on with the normal time lag. Our EMEA & APAC business is increasingly seen as the partner of choice due to our unrivalled product portfolio and our leadership and investment in innovation, sustainability, quality and service.

“In our Latin American region, during the third quarter, we announced our agreement to acquire the containerboard assets of CMPC in Chile. This acquisition further strengthens our leadership presence in Latin America as the only pan regional supplier, where we continue to see many opportunities for development. For the quarter, the region reported Adjusted EBITDA of $126 million and an Adjusted EBITDA margin of 21.4%.

¹ Adjusted EBITDA, Adjusted EBITDA Margin and Adjusted Basic EPS are non-GAAP measures. See the “Non-GAAP Financial Measures and Reconciliations” below for discussion and reconciliation of these measures to the most comparable GAAP measures.

"For full year 2026, we now estimate our Adjusted EBITDA² to be approximately $4.7 billion. This expected outcome primarily reflects the continued and unprecedented cost inflation we are experiencing. For example, for the full year 2026 we expect to absorb approximately $700 million of additional freight and energy costs alone, significantly more than anticipated. We have, and are, implementing price increases to more than offset these costs, the full benefits of which we expect to realize into 2027. Against what has been a challenging operating environment I am very proud of the efforts of all our people who have set the foundation for continued progress into 2027 and beyond.”

Dividend

Smurfit Westrock plc announced today that its Board approved a quarterly dividend of $0.4523 per share on its ordinary shares. The quarterly dividend of $0.4523 per ordinary share is payable on December 10, 2026 to shareholders of record at the close of business on November 13, 2026.

Earnings Call

Management will host an earnings conference call today at 7:30 AM ET / 11:30 AM GMT to discuss Smurfit Westrock’s financial results. The conference call will be accessible through a live webcast. Interested investors and other individuals can access the webcast, earnings release, and earnings presentation via the Company’s website at www.smurfitwestrock.com. The webcast will be available at https://investors.smurfitwestrock.com/overview and a replay of the webcast will be available on the website shortly after the call.

Forward Looking Statements

This press release includes certain “forward-looking statements” (including within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) regarding, among other things, the plans, strategies, outcomes, outlooks and prospects, both business and financial, of Smurfit Westrock, the expected benefits of the completed combination of Smurfit Kappa Group plc (re-registered as Smurfit Kappa Group Limited) (“Smurfit Kappa”) and WestRock Company (“WestRock”) (the “Combination”) (including, but not limited to, synergies, as well as our scale, geographic reach and product portfolio), our medium-term plan, demand outlook, operating environment and the impact of unprecedented inflation and energy prices, announced closures and additional economic downtime, our ability to increase prices to offset elevated costs and pass through such increases and any other statements regarding Smurfit Westrock's future expectations, beliefs, plans, objectives, results of operations, financial condition and cash flows, or future events, outlook or performance.

Statements that are not historical facts, including statements about the beliefs and expectations of the management of Smurfit Westrock, are forward-looking statements. Words such as “may”, “will”, “could”, “should”, “would”, “anticipate”, “intend”, “estimate”, “project”, “plan”, “believe”, “expect”, “target”, “prospects”, “potential”, “commit”, “forecasts”, “aims”, “considered”, “likely” and variations of these words and similar future or conditional expressions are intended to identify forward-looking statements but are not the exclusive means of identifying such statements. While the Company believes these expectations, assumptions, estimates and projections are reasonable, such forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which are beyond the control of the Company. By their nature, forward-looking statements involve risk and uncertainty because they relate to events and depend upon future circumstances that may or may not occur. Actual results may differ materially from the current expectations of the Company depending upon a number of factors affecting its business, including risks associated with the integration and performance of the Company following the Combination. Important factors that could cause actual results to differ materially from plans, estimates or expectations include: our ability to deliver on our medium-term plan; our ability to increase prices to offset elevated costs and pass through such increases; changes in demand environment; our ability to deliver on our closure plan and associated efforts; our future cash payments associated with these initiatives; potential future cost savings associated with such initiatives; the amount of charges and the timing of such charges or actions described herein; potential future impairment charges; accuracy of assumptions associated with the charges; economic, competitive and market conditions generally, including macroeconomic uncertainty, customer inventory rebalancing, the impact of inflation and increases in energy, raw materials, shipping, labor and capital equipment costs; geo-economic fragmentation and protectionism such as tariffs, trade wars or similar governmental actions affecting the flows of goods, services or currency (including the implementation of tariffs by the U.S. federal government and reciprocal tariffs and other protectionist or retaliatory measures governments in Europe, Asia, and other countries have taken or may take in response); the impact of prolonged or recurring U.S. federal government shutdowns and any resulting volatility in the capital markets or interruptions in the Company’s access to capital; the impact of public health crises, such as pandemics and epidemics and any related company or governmental policies and actions to protect the health and safety of individuals or governmental policies or actions to maintain the functioning of national or global economies and markets; reduced supply of raw materials, energy and transportation, including from supply chain disruptions and labor shortages; developments related to pricing cycles and volumes; intense competition; the ability of the Company to successfully recover from a disaster or other business continuity problem due to a hurricane, flood, earthquake or other weather-event, terrorist attack, war, pandemic, security breach, cyber-attack, power loss, telecommunications failure or other natural or man-made events, including the ability to function remotely during long-term disruptions; the Company's ability to respond to changing customer preferences and to protect intellectual property; the amount and timing of the Company's capital

² Adjusted EBITDA is a non-GAAP financial measure. We have not reconciled Adjusted EBITDA outlook to the most comparable GAAP outlook because it is not possible to do so without unreasonable efforts due to the uncertainty and potential variability of reconciling items, which are dependent on future events and often outside of management’s control and which could be significant. Because such items cannot be reasonably predicted with the level of precision required, we are unable to provide an outlook for the comparable GAAP measure (net income).

expenditures; risks related to international sales and operations; failures in the Company's quality control measures and systems resulting in faulty or contaminated products; cybersecurity risks, including threats to the confidentiality, integrity and availability of data in the Company's systems; works stoppages and other labor disputes; the Company’s ability to establish and maintain effective internal controls over financial reporting in accordance with the Sarbanes Oxley Act of 2002, as amended, and remediate any weaknesses in controls and processes; the Company's ability to retain or hire key personnel; risks related to sustainability matters, including climate change and scarce resources, as well as the Company's ability to comply with changing environmental laws and regulations; the Company's ability to successfully implement strategic transformation initiatives; results and impacts of acquisitions by the Company, including delays or failure to complete pending transactions, the incurrence of significant transaction costs, adverse market reactions, and regulatory or legal challenges; the Company's significant levels of indebtedness; the impact of the Combination on the Company's credit ratings; the potential impairment of assets and goodwill; the availability of sufficient cash to distribute dividends to the Company's shareholders in line with current expectations; the scope, costs, timing and impact of any restructuring of operations and corporate and tax structure; evolving legal, regulatory and tax regimes; changes in economic, financial, political and regulatory conditions in Ireland, the United States and elsewhere, and other factors that contribute to uncertainty and volatility, natural and man-made disasters, civil unrest, geopolitical uncertainty, and conditions that may result from legislative, regulatory, trade and policy changes associated with the current or subsequent Irish, U.S. or other administrations; legal proceedings instituted against the Company; actions by third parties, including government agencies; the Company's ability to promptly and effectively integrate Smurfit Kappa's and WestRock's businesses; the Company's ability to achieve the synergies and value creation contemplated by the Combination; the Company's ability to meet expectations regarding the accounting and tax treatments of the Combination, including the risk that the Internal Revenue Service may assert that the Company should be treated as a U.S. corporation or be subject to certain unfavorable U.S. federal income tax rules under Section 7874 of the Internal Revenue Code of 1986, as amended, as a result of the Combination; other factors such as future market conditions, currency fluctuations, the behavior of other market participants, the actions of regulators and other factors such as changes in the political, social and regulatory framework in which the Company's group operates or in economic or technological trends or conditions, and other risk factors included in the Company’s filings with the Securities and Exchange Commission, including the Company’s most recent Annual Report on Form 10-K. The Company’s forward-looking statements speak only as of the date of this press release or as of the date they are made. Neither the Company nor any of its associates or directors, officers or advisers provides any representation, assurance or guarantee that the occurrence of the events expressed or implied in any such forward-looking statements will actually occur. You are cautioned not to place undue reliance on these forward-looking statements. Other than in accordance with its legal or regulatory obligations, the Company is under no obligation, and the Company expressly disclaims any intention or obligation, to update or revise publicly any forward-looking statements, whether as a result of new information, future events or otherwise.

About Smurfit Westrock

Smurfit Westrock is a leading provider of paper-based packaging solutions in the world, with approximately 96,000 employees across 40 countries.

Condensed Consolidated Statements of Operations (Unaudited)

(in millions, except per share data)

Segment Information

We report our financial results of operations in the following three reportable segments:

Segment profitability is measured based on Adjusted EBITDA, defined as income before income taxes, unallocated corporate costs, depreciation, depletion and amortization, interest expense, net, pension and other postretirement non-service income, net, share-based compensation expense, other expense, net, impairment and restructuring costs, transaction and integration-related expenses associated with the Combination and other specific items that management believes are not indicative of the ongoing operating results of the business.

Financial information by segment is summarized below (in millions, except margins).

³ Adjusted EBITDA / Net sales (aggregate)

Condensed Consolidated Statements of Cash Flows (Unaudited)

(in millions)

Non-GAAP Financial Measures and Reconciliations

Smurfit Westrock reports its financial results in accordance with accounting principles generally accepted in the United States ("GAAP"). However, management believes certain non-GAAP financial measures provide Smurfit Westrock’s Board of Directors, investors, potential investors, securities analysts and others with additional meaningful financial information that should be considered when assessing its ongoing performance. Smurfit Westrock management also uses these non-GAAP financial measures in making financial, operating and planning decisions, and in evaluating company performance. Non-GAAP financial measures are not intended to be considered in isolation of or as a substitute for, or superior to, financial information prepared and presented in accordance with GAAP and should be viewed in addition to, and not as an alternative for, the GAAP results. The non-GAAP financial measures we present may differ from similarly captioned measures presented by other companies. Smurfit Westrock uses the non-GAAP financial measures “Adjusted EBITDA”, “Adjusted EBITDA Margin” and “Adjusted Basic Earnings Per Share” (referred to as “Adjusted Basic EPS”). We discuss below details of the non-GAAP financial measures presented by us and provide reconciliations of these non-GAAP financial measures to the most directly comparable financial measures calculated in accordance with GAAP.

Definitions

Smurfit Westrock uses the non-GAAP financial measures “Adjusted EBITDA” and “Adjusted EBITDA Margin” to evaluate its overall performance. The composition of Adjusted EBITDA is not addressed or prescribed by GAAP. Smurfit Westrock defines Adjusted EBITDA as net income before income tax expense, depreciation, depletion and amortization, interest expense, net, pension and other postretirement non-service income, net, share-based compensation expense, other expense, net, impairment and restructuring costs, transaction and integration-related expenses associated with the Combination and other specific items that management believes are not indicative of the ongoing operating results of the business.

Management believes Adjusted EBITDA and Adjusted EBITDA Margin measures provide Smurfit Westrock’s management, Board of Directors, investors, potential investors, securities analysts and others with useful information to evaluate Smurfit Westrock’s performance relative to other periods because it adjusts out non-recurring items that management believes are not indicative of the ongoing results of the business. Adjusted EBITDA Margin is calculated as Adjusted EBITDA divided by Net Sales.

Smurfit Westrock uses the non-GAAP financial measure “Adjusted Basic EPS”. Management believes this measure provides Smurfit Westrock’s management, Board of Directors, investors, potential investors, securities analysts and others with useful information to evaluate Smurfit Westrock’s performance because it excludes impairment and restructuring costs, transaction and integration-related expenses associated with the Combination and other specific items that management believes are not indicative of the ongoing operating results of the business. Smurfit Westrock and its Board of Directors use this information when making financial, operating and planning decisions and when evaluating Smurfit Westrock’s performance relative to other periods. Smurfit Westrock believes that the most directly comparable GAAP measure to Adjusted Basic EPS is Basic earnings per share attributable to common shareholders (referred to as “Basic EPS”).

Reconciliations to Most Comparable GAAP Measure

Set forth below is a reconciliation of the non-GAAP financial measures Adjusted EBITDA and Adjusted EBITDA Margin to Net Income and Net Income Margin, the most directly comparable GAAP measures, for the periods indicated (in millions, except margins).

Set forth below is a reconciliation of the non-GAAP financial measure Adjusted Basic EPS to Basic EPS, the most directly comparable GAAP measure for the periods indicated.

⁴ Net Income / Net Sales

⁵ Adjusted EBITDA / Net Sales