Mitchell was born in El Paso, Texas and was raised on a variety of military bases in places like Kansas, New Mexico, Pennsylvania, and Germany.

His mother, Joan Cameron Mitchell, a native of Glasgow, Scotland, immigrated to the United States as a young woman to become an art teacher.

[4] He appeared in the original cast of John Guare's Six Degrees of Separation (both off- and on-Broadway), and starred in Larry Kramer's off-Broadway sequel to The Normal Heart, The Destiny of Me, for which he received an Obie Award[5] and a Drama Desk nomination.

[6] Mitchell's early television work includes guest-starring roles in Daybreak, MacGyver, Head of the Class, Law & Order, The Twilight Zone, Freddy's Nightmares, The Equalizer, Our House, The Dreamer of Oz: The L. Frank Baum Story, and The Stepford Children.

He was a regular cast member on the 1996 Fox sitcom Party Girl, and was the long-running voice of Sydney, the animated kangaroo mascot of Dunkaroos snack cookies.

[citation needed] Starring and co-starring film roles include a homicidal new waver in Band of the Hand (1986), a Polish immigrant violinist in Misplaced (1990), and a teen Lothario poet in Book of Love (1990).

Mitchell is a founding member of the Drama Department Theater Company, for which he adapted and directed Tennessee Williams' Kingdom of Earth starring Cynthia Nixon and Peter Sarsgaard.

[10] After the success of Hedwig, Mitchell expressed an interest in writing, directing, and producing a film that incorporated explicit sex in a naturalistic and thoughtful way, without using "stars".

He directed the 2010 film Rabbit Hole, starring Nicole Kidman (in an Oscar-nominated performance) and Aaron Eckhart, adapted from David Lindsay-Abaire's Pulitzer Prize-winning play of the same name about a couple dealing with the loss of their four-year-old son.

He directed videos for Bright Eyes' "First Day of My Life" (featuring Secret Garden co-star Alison Fraser)[14] and the Scissor Sisters' "Filthy/Gorgeous";[15] the latter was banned from MTV Europe for its explicitly sexual content.

[16] In 2012, Mitchell wrote and produced a narrative short film for Sigur Rós titled "Seraph", directed by animator Dash Shaw.

Mitchell's punk era YA romance film How to Talk to Girls at Parties starring Elle Fanning, Alex Sharp, and Nicole Kidman was released by A24 in spring 2018.

In 2019, John released his latest musical, co-written with Bryan Weller, as a fictional podcast series titled Anthem: Homunculus starring himself, Glenn Close, Patti Lupone, Cynthia Erivo, Denis O'Hare, Nakhane, Laurie Anderson, Alan Mandell, Marion Cotillard, Ben Foster, and Madeline Brewer presented by the Luminary Podcast Network.

Mitchell's "distance-defying, community-built benefit album" New American Dream (Parts 1 and 2) was released September 4, 2020, including collaborations with Ezra Furman, Alynda Segarra of Hurray for the Riff Raff, Stephen Trask, Jamie Stewart of Xiu Xiu, Wynton Marsalis, Jeremiah Lloyd Harmon, Catherine Russell and Leland benefitting a COVID food bank, a trans justice group and the Dr. MLK Scholarship Trust Fund.