Wilson Sonsini was founded in 1961 as
McCloskey, Wilson & Mosher in Palo Alto, California, with attorneys
Paul N. "Pete" McCloskey Jr., John Arnot Wilson, and Roger Laurence Mosher as the name partners. The firm since launch has primarily been focused on the representation of emerging technology companies and venture capitalists.
Lawrence W. "Larry" Sonsini joined the firm in 1966 and after McCloskey left for Congress the firm became
Wilson, Mosher & Sonsini. In 1969, the firm helped form
Mayfield Fund, a venture capital firm. In 1970,
John B. Goodrich, who held a J.D. from the
University of Southern California (1966) and an LL.M. in taxation from
New York University (1970), joined the firm as its eighth or ninth lawyer and founded its Tax Department. The following year,
Mario M. Rosati, a graduate of
Boalt Hall, joined to establish the firm's Trust and Estates practice; he had earlier incorporated semiconductor equipment company
Aehr Test Systems in 1977 and served on its board for 45 years. The firm was also involved in representing companies in the semiconductor industry like,
LSI Logic,
Altera,
Cirrus Logic,
Lattice Semiconductor, and
Cypress Semiconductor. In late 1998, the firm opened its first national office, in
Kirkland, Washington, led by partner Patrick Schultheis. Within the next few years, the firm opened offices in Austin, Texas; San Francisco; Northern Virginia; New York; and San Diego. In 2005, Wilson Sonsini launched an office in China and enhanced its New York office. In 2006 the firm relocated its Northern Virginia lawyers to
Washington, D.C., to be closer to government regulators and the firm eventually moved its Kirkland office to Seattle. The firm also opened offices in Los Angeles, Boston, Wilmington, Delaware, Salt Lake City, Utah, and Boulder, Colorado. Internationally, the firm has offices in London, Brussels, Beijing (shut down in 2025), Hong Kong, and Shanghai. In 1994, Wilson Sonsini represented
Netscape Communications in its IPO, in addition to representing several other companies that, like Netscape, Infoseek, USWeb/CKS, and Inktomi. In 1999, when
VA Linux went public, the firm reaped $24.5 million as the value of the 100,000 shares that the firm held ballooned in value. Other IPOs that enriched the firm because of its equity stake were those of
Ask Jeeves,
Google, and online grocer
Webvan. With the downturn in the dotcom economy, however, Wilson Sonsini had to make a number of adjustments; 100 support staff and 60 associates were laid off—about 10% of its attorneys. Better times eventually returned. In 2004, the firm advised
Google on its $2.7 billion IPO. In February 2005, the firm announced that Larry Sonsini, 64, who had been chief executive for more than 20 years, stepped aside, and named
John Roos, a 20-year veteran partner who had led representations of young companies and entrepreneurs, as chief executive officer. After becoming CEO, Roos steered Wilson Sonsini beyond the burst tech bubble toward a broader client portfolio and a global presence. In 2009, after President Obama appointed Roos as
U.S. Ambassador to Japan, Steven E. Bochner, a 28 year veteran partner at the firm, succeeded Roos as CEO. Wilson Sonsini represented
Twitter in the transaction involving
Elon Musk's $44 billion take-private bid. In May 2025, Wilson Sonsini sold SixFifty, its legal tech unit, to
Paychex, an American payment technology company, in an all-cash deal worth between $70 million and $85 million. Wilson Sonsini is also serving as outside counsel for Google in its
antitrust litigation before the U.S. Department of Justice. The firm’s partner Susan Creighton, a longtime advisor to Google, contributed to an internal memo at Netscape that helped prompt the U.S. DOJ’s investigation of Microsoft in the 1990s. Creighton also led outside counsel efforts during Google’s 2013 settlement of an FTC antitrust inquiry. Douglas Clark led the firm, from 2012 until retirement in August 2026, when Caz Hashemi and Megan Baier will helm Wilson Sonsini as co-managing partners. ==Notable people==