FacultyFaculty/Author Profile

Michael J. O'Brien


New York, NY, USA

Michael O'Brien is a partner in the Corporate Practice Group. His practice focuses primarily on mergers and acquisitions and private equity transactions. He has represented private equity firms, financial institutions and strategic clients in public and private investment transactions for over twenty years.


Mr. O’Brien’s private equity experience ranges from start-up capital investments to large leveraged buyouts of established operating companies, including joint strategic/private equity bidding groups. He has represented private and public companies in general corporate and securities matters, financing transactions and domestic and international joint ventures. Recent transactions include:

Represented Citibank, N.A., in the sale of the Diners Club network to Discover Financial Services. The transaction involved Diners Club network operations worldwide.
  • Represented Blum Capital Partners in PIPEs investments in financial institutions.
  • Represented Morgan Stanley as financial advisor to Visicu, Inc., in connection with the public acquisition by Royal Philips Electronics.
  • Represented Caremark Rx, Inc., in its $26 billion merger with CVS Corporation.
Prior to joining WilmerHale, Mr. O'Brien was Managing Partner of the New York office of King & Spalding LLP. He was responsible for overall operations of the office, including key client development and growth strategy. During 1999 and 2000, he served as Executive Vice President and General Counsel of an integrated aluminum producer, where he was responsible for strategic, legal and operational matters. Previously, Mr. O'Brien was a partner at O'Sullivan Graev & Karabell, LLP for ten years, where he acted as outside general counsel to several of the firm's major clients. He began his legal career as an associate at Cravath, Swaine & Moore.

Professional Activities

Mr. O'Brien is a member of the Board of Directors of the Polytechnic Institute of NYU; the Lincoln Center Consolidated Corporate Fund's Leadership Committee; and the Board of Directors of the Friends of the Highline. He is a member of the Partnership for New York City. He also served on the advisory committee of The Hetrick-Martin Institute, and was a member of the Executive Committee and the Board of Directors of the Aluminum Association.

Mr. O'Brien is a member of the Association of the Bar of the City of New York, the New York State Bar Association and the American Bar Association.

Honors and Awards
  • Selected by his peers for inclusion in The Best Lawyers in America 2008.
  • 2009, 2010 and 2011 in the area of corporate law (private funds)

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