Dean's parents are Lance and Vicky O'Gorman. His father is a well-known landscape painter in New Zealand who regularly exhibits his work in several galleries. His younger brother Brett is also an actor, and was part of the legendary Auckland comedy trio ...GARY.
Dean began acting as a boy after he was discovered in a school production, and he appeared in the made-for-TV movies Raider of the South Seas and The Rogue Stallion. Commercials and acting roles continued to come his way while he was in high school, and he eventually gave up the idea of entering art school to pursue acting full time. He studied acting at Rangitoto College in Auckland.
Dean played several roles for Pacific Renaissance Pictures in the late 1990s, including Iloran and Ruun in Hercules: The Legendary Journeys and Orion/Homer and Wiglaf in Xena: Warrior Princess. He gained a world-wide following as Young Iolaus, a role he played in three episodes of Hercules, in the made-for-TV movie Young Hercules, and in the 50-episode series Young Hercules in 1998-1999.
Dean has appeared regularly on New Zealand television, including the soap opera Shortland Street, adventure series The Legend of William Tell, and police drama Duggan. His made-for-TV movies and miniseries include The Chosen, Money for Jam, and Lawless III: Beyond Justice. The made-for-TV movies Bonjour, Timothy, Return to Treasure Island, Doomrunners, and Fearless showed in wider markets, including the US.
Dean also starred in the short films Little Samurai and Siren. He has performed live with Theatresports in Auckland and appeared in Summer Shakespeare's production of "The Winter's Tale".
Dean has starred in feature films that have been popular at film festivals around the world. In 1998, he starred in the drama When Love Comes, a film selected for the 1999 Sundance Film Festival. The post-modern thriller Snakeskin (2001) premiered at the 2001 Cannes Film Festival market, and premiered in New Zealand at the New Zealand Film Festival. Toy Love, Kiwi director Harry Sinclair's sexy screwball comedy with a contemporary twist had its world premiere at the 2002 Cannes Film Festival market and screened at film festivals around the world before a successful commercial run in New Zealand cinemas.
Dean starred as Luke Morgan in seasons 4 and 5 of the hit Australian TV series McLeod's Daughters. The series is syndicated around the world on the Hallmark Channel and other local cable channels. While he was living in Australia he also starred in a production of Stephen Belber's play "Tape" at Sydney's Tap Gallery in March, 2003 and appeared in the Aussie TV series All Saints and MDA (Medical Defence Australia) and in the Aussie-made SciFi Network series Farscape.
Dean was back in Auckland in early 2004, starring in the hit Kiwi sitcom Serial Killers.
Dean starred in the world premiere of Michael Galvin's new play "The Ocean Star" for the Auckland Theatre Company from 28 September through 21 October, 2006.