Early life and education
Kirk was born in Salem, Oregon, to a mother of Russian-Jewish descent and a father with Danish and English heritage.1 As a child he moved with his family to Union, Washington, where he attended Hood Canal Elementary School on a Native American reservation.1 He knew he wanted to perform from an early age and made his acting debut at age seven in a local college production.1 At age twelve or thirteen his family relocated to Minneapolis, Minnesota, where he attended high school and trained with the Children's Theatre Company, one of the country's leading youth theater organizations.1
After high school Kirk moved to New York City, where he performed in several rock bands, most notably The Dimestore Darlings,1 before committing to acting full time. He completed a two-year conservatory program at Circle in the Square Theatre School, one of Broadway's most respected acting training programs.1
Career
Theatre
Kirk built his early reputation on the New York stage. He made his Broadway debut in Frank Gilroy's Any Given Day at the Longacre Theatre1 and received wide attention for originating the role of Bobby Brahms in Terrence McNally's Love! Valour! Compassion! (1994-1995), a production he also brought to film in 1997.1 He played Stephen Hoffman in Old Wicked Songs on Broadway in 1996-1997 and earned a Lucille Lortel Award for Outstanding Featured Actor for Ten Unknowns in 2001.1 In 2012 he appeared on Broadway as Trip Wyeth in Jon Robin Baitz's Other Desert Cities.1
Television
Kirk's first significant television lead was in the WB drama-comedy Jack & Jill (1999-2001), where he appeared in 32 episodes.3 His international breakthrough came with the HBO miniseries Angels in America (2003), directed by Mike Nichols. Kirk played Prior Walter, a gay New Yorker living through the AIDS crisis in the 1980s, across all six parts of Tony Kushner's epic. The performance earned him a Primetime Emmy Award nomination for Outstanding Supporting Actor in a Miniseries or a Movie1 and a Satellite Award win for Best Supporting Actor.1
His most sustained television work followed as Andy Botwin, the ne'er-do-well brother-in-law of a suburban marijuana dealer, in the Showtime dark comedy Weeds (2005-2012). Kirk appeared in all 99 episodes across eight seasons3 and received multiple award nominations including SAG Award nominations with the ensemble and a Golden Globe nomination.1 He also won a Satellite Award for Best Actor in a Comedy Series in 2008 for this role.1
Subsequent series credits include a 9-episode run as the lead of the NBC sitcom Animal Practice (2012); a recurring role in the WGN period drama Manhattan (2015); a guest arc on the FXX dark comedy You're the Worst (2015); 6 appearances as Charlie Bingham on Modern Family (2010-2015); 18 episodes as a series regular on the Showtime drama Kidding (2018-2020) opposite Jim Carrey; and 11 episodes as prosecutor Hamilton Burger in HBO's Perry Mason (2020-2023), a role that was upgraded to series regular for the second season.3 He played right-wing populist politician Jeryd Mencken in 5 episodes of HBO's Succession (2021-2023), a recurring antagonist during the show's final seasons.3
In 2024 he joined the cast of AMC's Interview with the Vampire as Raglan James, the devious Talamasca psychic who serves as a major antagonist, reprising the character in the connected spin-off Talamasca.3 In 2025 he guest starred on the CBS comedy-fantasy Ghosts as Tad, the Mayor.3
Film
Kirk reprised his stage role as Bobby Brahms in the 1997 film adaptation of Love! Valour! Compassion!, directed by Joe Mantello.1 Other film credits include Ask the Dust (2006), Molly's Game (Aaron Sorkin, 2017), and Vice (Adam McKay, 2018), where he played White House aide Scooter Libby.3 He also voiced Hal Jordan, the Green Lantern, in the DC animated film Justice League: War (2014).3
Ghostbusters
Ghostbusters: Answer the Call (2016)
Kirk plays Phil Hudson in Paul Feig's 2016 reboot. Phil Hudson is Erin Gilbert's romantic partner, a fellow Columbia University academic who proves unsympathetic to her paranormal research interests. The character was cut entirely from the theatrical release of the film; he appears only in the extended edition, which runs approximately fifteen minutes longer than the theatrical version.4
Kirk appears in three restored scenes in the extended cut. In the first, Phil greets Erin at a Columbia administrative gathering and introduces her to physicist Phyllis Adler, a guest lecturer whom Erin admires, though the dynamic makes clear that both Phil and Adler regard Erin's field of study as beneath serious academic consideration. In the second scene, following Erin's dismissal from Columbia, Phil ignores her as she leaves the campus. In the third and final scene, Phil and Erin argue about her decision to pursue ghost investigation, and their relationship ends.
The role was uncredited in the film's original release materials.5