In 1954, the family moved to California. Boies graduated from Fullerton Union High School in Fullerton, California. Boies attended the University of Redlands from 1960 to 1962, received a B.S. degree from Northwestern University in 1964, a J.D. degree magna cum laude from Yale Law School in 1966 and an LL.M. degree from New York University School of Law 1967; he was awarded an honorary LL.D. from the University of Redlands in 2000.

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.

In his 2001 book, prosecutor and author Vincent Bugliosi criticized Boies’ abilities as a trial lawyer, arguing that Boies “wasn’t forceful or eloquent at all in making his points” in Bush v. Gore. “[A]lthough he seemed to have a very good grasp of the facts, he seemed completely incapable of drawing powerful, irresistible inferences from those facts that painted his opposition into a corner”.

In 2017, Boies’ firm reportedly directed private intelligence company Black Cube to spy on alleged victims of Harvey Weinstein’s sexual abuse and on reporters who were investigating Weinstein’s actions. Over the course of a year, Weinstein had Black Cube and other agencies “target,” or collect information on, dozens of individuals, and compile psychological profiles that sometimes focused on their personal or sexual histories.