Stephen started acting in small, local theaters when he was just 11 years old. In his senior year of high school, MTV asked him to appear in a television show that would document his life, as well as his friends lives, in Laguna Beach. After high school, he attended San Francisco State University, but eventually decided not to continue. Stephen is best known for portraying himself on Laguna Beach: The Real Orange County. He has appeared on MTV's TRL numerous times.
- He enjoys surfing.
- Had an on/off relationship with Kristin Cavallari when he was in high school.
- He's the ex-boyfriend of Hayden Panettiere.
- He's also the ex-boyfriend of Chelsea Kane, who portrayed Tara Richards.
- He's close friends co-stars James Lafferty and Robert Buckley.
- He's good friends with Lauren Conrad.
- He was a groomsman at the wedding of co-star Lee Norris (Mouth McFadden).
- Both Stephen and co-star Tyler Hilton (Chris Keller) were in a Taylor Swift music video.
- Stephen is half Italian and half American.
- He worked in a surf shop before graduating from Laguna Beach High School.
- He attended San Francisco State University for 1 year (04-05) and his major was radio and television. Coletti decided not to return SFSU. Instead he moved to Los Angeles to pursue his acting career.