Yoshino graduated from Phillips Exeter Academy (1987) and Harvard, obtaining a B.A. in English literature summa cum laude in 1991. Between undergraduate years Yoshino worked as an aide for various members of the Japanese Parliament. He moved on to Magdalen College at Oxford as a Rhodes Scholar, attaining a M.Sc. in management studies (industrial relations) in 1993. In 1996 he earned a J.D. from Yale, where he was an editor of the Yale Law Journal.

He was soon published in multiple major law reviews. From 1996 to 1997 Yoshino served as a law clerk for federal appellate judge Guido Calabresi of the U.S. Court of Appeals for the Second Circuit. In 1998 he received a tenure-track position at Yale Law School as an associate professor, and in 2003 the school bestowed a full professorship. In 2006 he was named the inaugural Guido Calabresi Professor of Law.

Yoshino is also a prolific author in numerous periodicals and newspapers, including The New York Times, The Washington Post, Los Angeles Times, The Boston Globe, The Village Voice, The Nation, The Advocate, Slate, and FindLaw. Additionally, he is active as a speaker at various conferences on an assortment of legal and social issues. Yoshino is an expert guest on various public and commercial television and radio programs.

His book The Hidden Assault on Our Civil Rights was published in 2006. It is a mix of argument intertwined with pertinent biographical narratives.

Major areas of interest include social dynamics, conformity and assimilation, as well as queer (LGBT) and personal liberty issues. He has been a co-plaintiff in cases related to his specialties. A Japanese American, and openly gay man, Yoshino also writes poetry for personal enjoyment or at least as yet has not published.

During the 2006-2007 and 2007-2008 school years, he served as a visiting professor at New York University School of Law, and in February 2008 he accepted a full-time tenured position as the Chief Justice Earl Warren Professor of Constitutional Law.