A young, red-haired actor with a knack for making even the creepiest characters endearing, Green began his acting career with commercials at the age of six. His first film role was in 1984's "The Hotel New Hampshire" but the young actor's big break came four years later with a starring role in "Radio Days", playing Little Joe, a character often considered to be Woody Allen's rendering of himself as a young boy. His performances in "Can't Buy Me Love" (1987), as Patrick Dempsey's destructive and demented younger brother, "Big Business" (1988), as Bette Midler's psychotic son, and "Austin Powers: International Man of Mystery" (1997), as Dr. Evil's troubled progeny, further showcased his talent. Formerly a regular on such short-lived series as "Good and Evil" (ABC, 1991), "The Byrds of Paradise" (ABC, 1994) and "Temporarily Yours" (CBS, 1997), he was also featured in the 1990 ABC miniseries "Stephen King's IT", playing the young version of Harry Anderson's character. Green, however, reached his widest audience portraying the sweetly awkward musician/werewolf Oz who is romantically attached to Buffy's best friend Willow on the hit show "Buffy, the Vampire Slayer" (The WB), a recurring role which became regular in the 1998-1999 season.

After his stint on "Buffy," Green went on to land several significant film roles. He reprised his role in the Austin Powers sequels of 1999 and 2002 and had parts in "America's Sweethearts" (2001) and "Rat Race" (2001). In 2002, Green starred along with Eugene Levy and Sarah Silverman in the FOX series which featured puppets as talking characters, "Greg the Bunny." While the show only lasted one season, it received favorable reviews and developed a loyal cult following. He then joined John Malkovich, Vin Diesel, Dennis Hopper and Barry Pepperin the mobster-comedy feature, "The Knockaround Guys" (2002).