Born in Oregon and raised on an Indian reservation, actor Justin Kirk started his career at a very young age. After studying at the Children's Theatre School in Minnesota, he lived in New York City working as a struggling actor and hotel bellboy. One of his first off-Broadway roles was Bobby Brahms, the blind younger lover of an aging choreographer in Terrence McNally's play Love! Valour! Compassion! This led to an Obie award, a career on Broadway, and a part in the 1997 feature film adaptation directed by Joe Mantello.
Kirk continued to work on-stage in New York and Los Angeles, helping to found the Drama Department theater company. In 1999, his interests turned toward television and film. In the straight-to-video independent film The Eden Myth, he played a young man whose father (Gil Rogers) arranges his marriage. He also starred in the barely released comedy Chapter Zero starring Dylan Walsh and Penelope Ann Miller. On television, he had a regular role on the WB sitcom Jack & Jill about mainstream twentysomethings living in New York City. He played the moderately intelligent Barto (a character not unlike Ross on Friends) who was always hanging around the slightly less-intelligent Mikey (a character not unlike Joey on Friends). In 2002, he appeared in Harry Shearer's pet project Teddy Bears' Picnic, an independent spoof of an exclusive men's retreat. The same year he played mental patient Morris Monk in Alec Carlin's Outpatient, marking his first leading role in a feature film. Kirk gained much more exposure the next year as main character Prior Walter in the six-hour television miniseries version of Tony Kushner's play Angels in America, first aired on HBO in December of 2003. Kirk continued to have success on cable television throughout the 2000s, most notably on Showtime's Weeds in the role of Andy Botwin, who becomes tangled in his suburban family's involvement in the marijuana trade (2005-2012).