Graham was born in Long Beach, California. One of his earliest roles was in the 1980 CBS mini series Scruples based on the Judith Krantz novel starring Lindsay Wagner. He was cast as a "hitman" on the television show Moonlighting co-starring opposite Bruce Willis.
He has played more than 38 TV roles and has also been in more than 40 movies.
As well as Alien Nation and Star Trek, Graham starred in a 2008 TV pilot styled after Sin City called Dead End City.
As well as starring as Detective Matthew Sikes in the television series Alien Nation (1989–1990), he resumed this role in the TV movies Alien Nation: Dark Horizon (1994), Alien Nation: Body and Soul (1995), Alien Nation: Millennium (1996), Alien Nation: The Enemy Within (1996), and Alien Nation: The Udara Legacy (1997).
Star Trek fans probably know him best from his more recent guest-starring roles on Star Trek: Enterprise as the recurring character Ambassador Soval, a Vulcan ambassador to Earth. He also guest-starred on Star Trek: Voyager (1995) once, playing Ocampan community leader Tanis in the season 2 episode Cold Fire. He plays a new role, Ragnar, in the fan production Star Trek: Of Gods and Men and continued this role in Star Trek: Renegades.
In 2015, Graham will reprise his role as Ambassador Soval, in the fan film Star Trek: Axanar.
His films include Hardcore, "The Hollywood Knights (1980)", All the Right Moves, The Arrogant, The Last Warrior, Robot Jox, Running Woman, Siren. Gary's most recent films are InAlienable, Action Hero and Dreams Awake. Graham made his directorial debut in the spring of 2007 with the film Interviews which he also wrote.
Graham also made appearances as the "smoking jacket guy" in the introduction and other scenes in the Internet gaming show The Jace Hall Show.
Graham plays Dr. David Macavoy in the web series UNIVERSAL DEAD. In late June, 2010 it was announced that Universal Dead will be made into a feature film.