Boies was an attorney at Cravath, Swaine & Moore, where he started upon law school graduation in 1966 and became a partner in 1973. He left Cravath in 1997 when a major client objected to his representation of the New York Yankees even though the firm itself had found no conflict. He left the firm within 48 hours of being informed of the client's objection and created his own firm, now known as Boies, Schiller & Flexner LLP. It is currently rated 23rd in "overall prestige" and 15th among New York law firms by Vault.com, a website on legal career information.