Alan Klein is a Partner with Simpson Thacher & Bartlett LLP, where he practices in the Corporate Department. Alan’s practice concentrates on mergers and acquisitions, shareholder activism and corporate governance matters.
Alan has represented Microsoft Corporation in connection with its $75 billion acquisition of Activision Blizzard, its $28.2 billion acquisition of LinkedIn, its $7.2 billion acquisition of Nokia’s phone business, its acquisition of Skype for $8.5 billion in cash from the investor group led by Silver Lake and in its investment in Barnes & Noble’s Nook business, as well as in its approach to Yahoo! Inc.
In addition, he recently represented the Board of Directors of Twitter in connection with the sale of Twitter to Elon Musk; Aetna’s Board of Directors in connection with CVS Health’s acquisition of Aetna for $78 billion; Cisco Systems’ in its $28 billion acquisition of Splunk; The ADT Corporation in its $15 billion sale to Apollo Group Management; Johnson Controls in the sale of its Scott Safety business to 3M for approximately $2 billion and Tyco International Ltd. in connection with a number of transactions, including its $20 billion merger with Johnson Controls, Inc.; its separation into three independent, publicly traded companies and the multibillion-dollar merger of its Flow Control business with Pentair, Inc.; its acquisition of Chemguard, Inc.; its $300 million acquisition of a 75% equity stake in privately held KEF Holdings Ltd.; its $2 billion cash and stock acquisition of Brink’s Home Security Holdings, Inc., now operating as Broadview Security and its sale of a majority interest in its Electrical & Metal Products business. He also represented Best Buy in a take-private offer by its founder and former chairman.
Alan has also been involved in many cross-border M&A transactions around the world during the last decade, including representing ChemChina in its $43 billion acquisition of Syngenta; Chinalco in its $12 billon investment in Rio Tinto plc; Gas Natural S.A. in its $30 billion bid for Endesa S.A.; Royal Ahold in connection with its merger of equals with Delhaize Group; ADT in its CAD $550 million acquisition of Protectron; Rinker Group Limited in connection with its $15 billion acquisition by Cemex S.A.B. de C.V.; Portugal Telecom S.A. in connection with the unsolicited offer made for it by Sonae S.A.; Gerdau S.A. in its acquisition of Quanex Corporation; Bavaria S.A., Latin America’s second-largest brewer, in its sale to SABMiller plc; Owens-Illinois Inc. in its acquisition of French packaging company BSN Glasspack from CVC Europe and in its disposition of Owens-Brockway Plastic Products Inc.; Merck & Co, Inc. in its tender offer for shares of Banyu, a Japanese pharmaceutical company; Telefonica Moviles S.A. in its acquisition of certain non-U.S. cellular phone companies from Motorola Inc. and Pechiney in its proposed three-way merger with Alcan Aluminum and Alusuisse.
Alan is the past Co-Chair of the International Bar Association’s Corporate and M&A Law Committee and for seven years he chaired the International Bar Association’s Annual International Mergers and Acquisitions Conference in New York City.
Alan, among other publications, authored a chapter entitled “Avoiding the Pitfalls and Reaping the Benefits of Cross-Border M&A Deals” in Structuring International M&A Deals: Leading Lawyers on Managing Mergers & Acquisitions in a Global Environment, published by Aspatore Books, a Thomson-Reuters business.
From 1994 to 1998, Alan was resident in the Firm’s London office, and worked on international transactions, including the merger of Glaxo plc and Wellcome plc; the acquisition of Affymax N.V. by Glaxo; the acquisition by Owens-Illinois, Inc. of the glass and packaging business of BTR plc; the acquisition of Yorkshire Electricity plc by American Electric Power and its partner New Century Energy, as well as initial public offerings by British, French, Italian, Norwegian and Swedish companies.
Alan joined the Firm in 1984 and became Partner in 1993. He served as Co-Head of the Firm’s Mergers and Acquisitions Practice from 2016 to 2021 and is a former member of the Firm’s Executive Committee. Alan currently serves on the board of a number of non-profit organizations, including Lawyers for Children, Montefiore Medical Center, The Jewish Theological Seminary and the Library of America. Alan received his B.A. with Honors in history in 1981 from Haverford College. He received his J.D., cum laude, from Harvard Law School in 1984.
Most recently, Alan was recognized among Lawdragon’s “Leading Dealmakers in America” in 2025. He was also recognized as one of The American Lawyer's 2023 "Dealmakers of the Year" for his work advising Twitter's Board of Directors in the company's $44 billion acquisition by Elon Musk. Alan was named a 2017 “M&A Trailblazer” by the National Law Journal. He was also named a 2012 MVP by Law360 for his leadership in M&A, including closing within one year several of the market’s most significant M&A deals. In addition, Alan was selected as a 2012 “Dealmaker of the Year” by The American Lawyer for leading the Simpson Thacher team representing Microsoft in connection with its $8.5 billion acquisition of Skype. He is recognized in Chambers Global: The World’s Leading Lawyers for Business, Chambers USA: America’s Leading Lawyers for Business, The International Who’s Who of Mergers and Acquisitions Lawyers, and The International Who’s Who of Corporate Governance Lawyers, as well as by IFLR1000 as a leading mergers and acquisitions lawyer.