Elliott became known in the mid-late 1980s, when he was a writer and performer on Late Night With David Letterman, playing an assortment of recurring oddball characters. In 1990, Elliott created and starred in his own sitcom, which was called Get a Life, about a 30-year-old paperboy named Chris Peterson who lived at home with his parents. Elliott's real-life father, Bob Elliott, appeared in the show as Chris' father. In 1993, Elliott teamed up with producer Brad Hall and directed a series of critically acclaimed short films that Elliott showed when appearing on Late Show with David Letterman. In 1994, Elliott became a cast member of Saturday Night Live. Also that year, Elliott starred in his first movie, Cabin Boy, which also featured a short appearance by Elliott's old boss, David Letterman, and was produced by Tim Burton.
His other television credits include the chowder taster on Throwdown with Bobby Flay, and the voice of Dogbert on the short-run show Dilbert for UPN. He played a serial killer in the series Third Watch in episodes 5 from season six. He played the role of Peter in the last three seasons of Everybody Loves Raymond and a role in a semi-autobiographical sitcom pilot for CBS, entitled You've Reached the Elliotts, playing a man who tries to balance a modest show business career with his home life. As well as multiple appearances on King of Queens Elliott made guest appearances on That '70s Show, According to Jim and How I Met Your Mother.
He is married and has two daughters, Bridey and Abby Elliot. Abby played the role of Jeanette Peterson, Ted's crazy girlfriend.