Balfour was born in Los Angeles, California, the son of Sharon, who works as a marriage and family counselor, and David Balfour, a chiropractor.He has a younger sister Tori. He is of Russian, French, and Native American descent . Balfour was engaged to actress Moon Bloodgoodbut reports recently suggest that he is single again. In January, 2008, he participated in a video for Barack Obama produced by Will.I.Am called Yes We Can and campaigned as a surrogate with Kal Penn

Balfour appeared on the kids TV show Kids Incorporated for one season in 1991. In 1997, he appeared in the pilot for Buffy the Vampire Slayer, as one of the show's very first victims. Years later, Balfour appeared as a dancer in the music video for the song "Fergalicious" by former Kids Incorporated castmate Fergie He appeared as a regular cast member in three short-lived TV shows. NBC's Hawaii was canceled after seven episodes in 2004, UPN's Sex, Love & Secrets was canceled after four episodes in 2005, and in March 2006, Balfour debuted as Brian Peluso on producer Dick Wolf's short-lived NBC crime drama, Conviction which lasted one season.

He starred in the 2003 remake of The Texas Chainsaw Massacre opposite Jessica Biel He played a minor character in several episodes of The O.C., as Eddie, Theresa's fiancee, and in the hit HBO show Six Feet Under, as Claire's thuggish boyfriend, Gabriel Dimas during most of the show's first season. In 2005, Balfour starred in the controversial and sexually explicit film Lie with Me.

Balfour is one of three actors to have appeared both in The O.C. and The West Wing. Balfour appeared in eight episodes of the first season of 24 as computer technician Milo Pressman in 2001. Five years later, Balfour reprised the role for nineteen episodes of 24's sixth season before leaving the show by his own request.

He is the face for the new Valentino male fragrance, Valentino V. He is set to star in CBS's new pilot Protect & Serve in 200.