Haim was born in Toronto, Ontario, Canada, the son of Judy, an Israeli-born computer operator, and Bernie Haim, who worked in sales.[1] Haim is Jewish. He was enlisted in acting lessons by his mother in an attempt to help him overcome his shyness. Haim, not particularly fascinated by acting, practiced other hobbies such as ice hockey, playing music on his keyboard and collecting comic books.

Haim first broke into mainstream acting playing the role of Larry in the Canadian family oriented comedy television series, The Edison Twins, which ran from 1982 through until 1986. Haim made his first cinematic appearance in the 1984 feature film, Firstborn, which also starred now well-known actors Sarah Jessica Parkerand Robert Downey Jr.In 1985, Haim appeared in minor roles in Secret Admirer and Murphy's Romance and starred in the leading role in a feature film version of Stephen King's novella, Silver Bullet, playing a paralytic boy alongside Gary Busey. Haim started to make a name for himself in the industry, notably by earning his first Young Artist Award as an Exceptional Young Actor Starring in a Television Special or Movie of the Week for the television movie A Time to Live.

On December 4, 2006, Haim began taping an improv/reality show with Corey Feldmantitled The Two Coreys. The show focuses on fictional versions of Haim and Feldman, with the comedy focusing on Feldman living with his wife, and Haim as a bachelor re-entering Feldman's life and shaking up his comfortable suburban lifestyle. The show premiered on the A&E Network on July 29, 2007, at 10:00 p.m. During an appearance (7/24/07) on The Opie and Anthony Show, Haim said he was once nearly 300 lbs. He claimed to lose 140 lbs. in 11 months by eating watermelon, cayenne pepper and hot water with lemon. Haim was recently nominated for the Viewer's Choice Awards at the 22nd Annual Gemini Awards in Canada for his role in "The Two Coreys." He was voted #8 in the category of "Favourite Canadian" on a TV Series (not eligible for a Gemini) for his role in the A&E show. Corey Feldmanand Corey Haim have signed on for a second season of the A&E Network reality show "The Two Coreys." On February 7, 2008, Haim ran a paid ad in a Hollywood trade publication, Variety, stating "This is not a stunt. I'm back. I'm ready to work. I'm ready to make amends." In February 2008, filming resumed in Vancouver for Lost Boys: The Tribe to include several scenes with Corey Haim reprising his role as Sam Emerson. Haim reversed his previous decision to not appear in this sequel. In 2009 Haim will appear in another sequel Crank 2: High Voltage.