Gant was born in Tampa, Florida, of Spanish, Italian, Cuban, Irish, and English descent. He was raised Baptist. He began acting in television commercials and joined the Screen Actors Guild at the age of ten in his home state of Florida. At the age of 11, he performed a soft-shoe routine with Bob Hope as part of Hope's USO tour.
He majored in English literature at the University of Pennsylvania and then studied law at Georgetown University Law Center. It was his career as a lawyer that brought him to Los Angeles when he accepted a position with the LA office of Chicago-based Baker & McKenzie. The international firm's Los Angeles office was closed soon after. Rather than continuing his career in law, he decided to focus on acting thereafter.
Gant is involved in a number of philanthropic organizations with a great deal of focus going to the issue of aging in the gay community. He currently resides in Los Angeles.
Between 2002 and 2005, Gant appeared on television in Showtime's Queer as Folk as Ben Bruckner, his best-known role to date. Prior to Queer as Folk, he appeared in recurring roles in Popular and Caroline in the City. Other guest appearances on television programs include Melrose Place, Ellen, Friends and Nip/Tuck, among others.
In June 2004, Gant starred in the short film Billy's Dad Is a Fudge-Packer!, an homage to 1950s educational films.
In 2005, he appeared in an episode of the television crime drama The Closer.
In 2007, Gant, Chad Allen and Judith Light acted and produced Save Me. The movie about the ex-gay movement was distributed by Mythgarden, the production company formed by Gant, Allen, and Christopher Racster in 2004.
In 2009, Gant appeared in Personal Affairs, a BBC Three-produced drama set in London's financial sector.
He also appeared in the independent films Special Delivery, The Contract, Fits and Starts and Marie and Bruce.
He plays the role of the Famous Director in the 2012 feature film Joshua Tree, 1951: A Portrait of James Dean. In 2011, Gant made a cameo appearance in season 1, episode 8 of TV Land's Happily Divorced.
In 2015, Gant played Zor-El, the titular character's father in Supergirl.
Gant supports such organizations as Services & Advocacy for GLBT Elders (SAGE) and Gay & Lesbian Elder Housing (GLEH).
He supported Hillary Clinton in her bid for the Democratic Party's Presidential nomination in 2008.Working – The Iron Worker
Taming of the Shrew (Uta Hagen's Acting Class DVD) – Petruchio
Little Shop of Horrors – The Dentist (et al.)
Grease – Danny Zuko; Kenicke
Whose Life is it Anyway? – John
The Mystery of Edwin Drood – Neville Landless / Victor Grinstead
The Mikado – Koko