The son of a musician, Feldman was the breadwinner of his family by age three, acting in scores of TV commercials. He was one of the regular little league playing boys on "The Bad News Bears" when it was turned into a CBS series from 1979-80, and, in 1982, he was the neglected rich boy neighbor on the short-lived syndicated series "Madame's Place". Feldman played Corey Cleaver, the next generation, in the update TV-movie "Still the Beaver" (CBS, 1983), but opted not to remain with the project when it was turned into a weekly series. He also made numerous guest appearances on episodics and co-starred in TV-movies. In 1989, Feldman played a key role in a CBS Schoolbreak Special "Fifteen and Getting Straight", in which his character was vehemently anti-drug, ironically while Feldman was having substance abuse problems. On the night of March 9, 1990, the actor was arrested by L.A. police after they had stopped his car in a seedy section of the city and found nine grams of heroin and cocaine. Feldman went into rehab and won a community service sentence for that arrest and a subsequent one. When Hollywood assumed him to have been rehabilitated, he played opposite Corey Haim (himself also a recovering substance abuser) in "Blown Away" (HBO, 1993), in which Feldman was the bad older brother who helps to frame Haim. In 1995, Feldman returned to TV series as a computer nerd on the short-lived CBS series "Dweebs".
Feldman's feature film work dates back to "Time After Time" (1979), in which he had a small role as a boy who encounters H.G. Wells at a museum in San Francisco. In 1984, he had a supporting role as a rambunctious neighborhood boy in "Gremlins" and also played Tommy in "Friday the 13th-The Final Chapter", a role which he again played, this time at age 12, in "Friday the 13th: a New Beginning" (1985). Feldman was "Mouth" the friend who claims to speak Spanish in "Goonies" (1985). He was Haim's wiser friend in "License to Drive" (1988) and Tom Hanks' adolescent neighbor in "The Burbs" (1989). He appeared again with Haim in "Dream a Little Dream" (1989) and also choreographed the dance sequences. In 1994, after rehab, he had a small role in "Maverick" and appeared with Haim in "National Lampoon's Last Resort". Feldman has continued to be featured in mostly direct-to-video fare (i.e., "A Dangerous Place" and "Voodoo", both 1995), but did land a supporting role in "Tales From the Crypt Presents: Bordello of Blood" (1996). Additionally, Feldman has provided the voice for Donatello in the "Teenage Mutant Ninja Turtles" animated series. Additionally, Feldman has provided the voice for Donatello in the "Teenage Mutant Ninja Turtles" animated series. Feldman has also pursued a music career, releasing the solo album "Former Child Actor" in 2002.
In 2003, Feldman shared a space with a group of some of America's best-remembered pop culture figures, in the WB reality series "The Surreal Life."