Gunn was born and raised in Washington, D.C. He is the son of Nancy (née Comfort) and George William Gunn, an FBI agent during the administration of FBI Director J. Edgar Hoover. Gunn was a champion swimmer throughout high school, and later attended the Corcoran College of Art and Design, receiving a BFA in sculpture.
Gunn, who identifies as gay, was raised in an intensely homophobic household and viewed homosexuals as predators. According to a video Gunn created for the It Gets Better Project, he attempted to commit suicide at the age of 17 by swallowing over 100 pills. He denied his sexual orientation until his early 20s, and did not share it with his family until he came out to his sister when he was 29.
After serving as director of admissions for the Corcoran, Gunn started working at Parsons in 1982, served as associate dean from 1989–2000, and then became Fashion Design Department chair in August 2000. He was credited with "retooling and invigorating the curriculum for the 21st century."
Gunn began appearing on Project Runway during its first season in 2004, and is known for his catchphrase "Make it work." Gunn received a Primetime Emmy Award in 2013 for Outstanding Host For A Reality Or Reality-Competition Program. Tim Gunn's Guide to Style, a reality show in which Gunn gives advice to the fashion-challenged, debuted in September 2007 on the Bravo television network. This show ran for a total of 16 episodes over two seasons. Then starting in January 2014 Tim was the host on a single 13 episode season of Lifetime's Under the Gunn. Gunn is an executive producer for Project Runway: Junior. He is also the teen designers' mentor.
Gunn also played a version of himself as a reporter for the fictional Fashion TV in two episodes of ABC's Ugly Betty in February 2007 and later guest starred on Drop Dead Diva in August 2009 as himself.
Gunn left Parsons in 2007 and joined Liz Claiborne, Inc. as the company's chief creative officer in March of that year.
In April 2007, Abrams Image Publishers released Gunn's book A Guide to Quality, Taste and Style, co-written with Kate Moloney, cover photo by Markus Klinko & Indrani. While on tour in Palm Springs, California, the nearby city of Palm Desert honored him with an official resolution declaring April 27, 2007 (the day of his visit) "Timothy M. Gunn Day". He was also presented with a certificate by the city of Palm Springs and a plaque by the nearby city of Rancho Mirage in recognition of his career achievements. From 2010 to 2015 Gunn published four additional books (listed below).
In May 2009, Gunn served as commencement speaker at the Corcoran College of Art and Design, and received an honorary doctorate from the institution.
He made sporadic appearances on The Late Late Show with Craig Ferguson's "Dear Aquaman" segments, helping or standing in for Aquaman (Ferguson), answering letters and dispensing advice.
He guest starred as Barney's personal tailor on several episodes of How I Met Your Mother.
Gunn guest starred as himself on the 6th episode of CW's fourth season of Gossip Girl, "Easy J".
In August 2007, "Tim Gunn's Podcast (a reality chamber opera)" by Jeffrey Lependorf premiered at the Cornelia Street Cafe in Manhattan. It received its first run one year later at New York International Fringe Festival.
Gunn appeared in a backup story in the first issue of Models Inc., a fashion-themed comic book miniseries published by Marvel Comics that debuted in September 2009 to coincide with New York City's style showcase. Gunn appeared on a variant cover of the issue illustrated by Phil Jimenez. In the series, which is written by Project Runway fan Mark Sumerak and illustrated by Jimenez, Gunn dons the Iron Man armor to foil an attack against the New York Fashion Museum.
Gunn appeared in the opening skit on the 62nd Primetime Emmy Awards to style Jimmy Fallon to look like Bruce Springsteen, from his Born in the U.S.A. album.
In 2014, he participated in Do I Sound Gay?, a documentary film by David Thorpe about stereotypes of gay men's speech patterns.
Gunn lives in Manhattan. In a 2006 interview with Instinct, Gunn stated that he had not been in a relationship since the early 1980s, following the abrupt end of a six-year relationship, and that he still loves his former partner, though they are not in contact.
Gunn came out as asexual in 2010 in an interview with People Magazine, saying "For a long time, I didn't know what I was. I knew what I wasn't: I wasn't interested in boys, and I really wasn't interested in girls." He mentioned that one of the reasons his long-term boyfriend left him was because of sex, and that he has "always been kind of asexual."
Gunn spoke about his celibacy in 2012. He later stated that he is unashamed of this fact saying, "Do I feel like less of a person for it? No… I’m a perfectly happy and fulfilled individual.” He said he started his self-imposed celibacy as AIDS began ravaging the gay community, and that he and many other people simply retreated from that danger.
Gunn is an outspoken critic of clothing designs using animal fur. In 2008, he narrated a video about rabbit fur farming in China for animal rights group PETA. He termed the treatment of animals used for fur as "egregiously irresponsible".
Gunn endorsed Christine Quinn's candidacy for Mayor of New York City in the 2013 mayoral election.Project Runway (2004–present)
Drinks with LX (2006)
Ugly Betty (2007)
Tim Gunn's Guide to Style (2007–2008)
American Dad! (2008)
The Replacements (2008)
Drop Dead Diva (2009)
Project Runway: All-Star Challenge (2009)
The Biggest Loser: Second Chances (2009)
How I Met Your Mother (2010–2014)
Sex and the City 2 (2010)
Gossip Girl (2010)
Teen Spirit (2011)
Gossip Girl (2011)
The Smurfs (2011)
The Revolution (2012)
The Cleveland Show (2012)
Sofia the First: Once Upon a Princess (2012)
Sofia the First (2013–present)
Sesame Street (2013)
Family Guy (2013)
Under the Gunn (2014)
Hollywood Game Night (2014)
Inside Amy Schumer (2015)
Project Runway: Junior (2015–present)
The Real O'Neals (2016)
Bill Nye Saves the World (2017)
Mickey and the Roadster Racers (2017)
BoJack Horseman (2017)
Gunn, Tim; Moloney, Kate (2007), Tim Gunn: A Guide to Quality, Taste & Style, Harry N. Abrams, Inc., ISBN 0-8109-9284-1
Gunn, Tim; Calhoun, Ada (September 2010), Gunn's Golden Rules: Life's Little Lessons for Making It Work, Gallery Books, ISBN 1-4391-7656-6
Gunn, Tim (May 2011), Shaken, Not Stirred, Tim Gunn, ASIN B004UN4L9E
Gunn, Tim; Calhoun, Ada (September 2012), Tim Gunn's Fashion Bible: The Fascinating History of Everything in Your Closet, Gallery Books, ISBN 978-1-4516-4387-9
Gunn, Tim (March 2015), Tim Gunn: The Natty Professor: A Master Class on Mentoring, Motivating, and Making It Work!, Gallery Books, ISBN 978-1476780061