

He also starred as Sky Masterson in the 1992 Broadway hit revival of Guys and Dolls. Gallagher appeared on Broadway with Glenn Close in Tom Stoppard's The Real Thing and made his feature film debut in the Taylor Hackford film The Idolmaker, but first achieved fame for his role in Steven Soderbergh's sex, lies, and videotape (1989). He studied acting at the William Esper Studio.

Gallagher graduated from Tufts University, where he was active in theater, appearing in such shows as Stephen Sondheim's Company and singing with the all-male a cappella group the Beelzebubs. He is of Irish Catholic background and was raised in Armonk, New York. Gallagher is the youngest of their three children. His mother, Mary Ann ( née O'Shea), was a bacteriologist, and his father, Thomas Francis Gallagher, Jr., was an advertising executive.
