Born in Zion, Illinois, Coleman is most famous for the role of Arnold Drummond on Diff'rent Strokes in 1978. The show lasted until 1986. Coleman had a congenital kidney defect known as nephritis that has halted his growth leading to his notably small stature (4' 8"), which has become his visual and acting trademark. He has had two kidney transplants, one in 1973 and one in 1984 and requires constant dialysis.
During the late-1970s and early-1980s, Coleman starred in a number of feature films and made-for-TV movies including On the Right Track, and the Kid With the Broken Halo. As he grew older, however, the value of his cuteness faded, and after the cancellation of Diff'rent Strokes his acting career declined sharply.
Coleman famously sued his own parents over misappropriation of his trust fund for $3.8 million and won a $1,280,000 rulling on February 23, 1993. He briefly owned a video game arcade in Fisherman's Village near Santa Monica, California.
Once paid $70,000 an episode, Coleman filed for bankruptcy in 1999. In 2001 he was employed as a a shopping mall security guard in the Los Angeles area. He occasionally appears in cameo roles, most of which refer to his earlier acting career.
Coleman appeared in court on November 2, 2000 charged with assault. He was ordered to pay bus driver Tracy Fields $1,665 for hospital bills resulting from a fight stemming from an attempt by her to get his autograph in a California mall. Coleman said he felt "threatened by her insistence" and punched her in the head.
Coleman was a candidate for governor in the 2003 California recall election. This campaign was coordinated by the free news weekly the East Bay Express. After Arnold Schwarzenegger announced his candidacy, Coleman stated that he would be voting for Schwarzenegger. Coleman placed 8th in a field of 135 candidates, receiving 14,242 votes.