Glenn Martin Christopher Francis Quinn was born May 28, 1970 in Dublin, Ireland. He was raised in Cabinteely, County Dublin, and attended Clonkeen College. In 1988 he moved to the United States of America with his mother and two sisters.

He did commercials for Pepsi and Ray-Ban, appeared in the music video for the Richard Marx song "Satisfied," and was an extra in the pilot of Beverly Hills, 90210, though is barely visible in the final broadcast version.

In 1991, Quinn had his first major role in a movie, Shout, which starred John Travolta and in which he shared an on-screen kiss with Gwyneth Paltrow. Later, one of Quinn's more visible roles was that of Mark Healy, Becky Conner's husband in Roseanne. While working on that show, Quinn took on the role as youngest son Cedric on the US & UK TV series Covington Cross.

Another role that brought Quinn into the spotlight was Allen Francis Doyle, a half-demon on the 1999 TV series Angel. Most of his roles had called for him to hide his Irish accent and fake an American one instead; this was his first opportunity to use his own Irish accent in an American TV show or movie. His last film work was on the critically acclaimed 2002 R.S.V.P..

In addition to acting, Quinn enjoyed collecting Star Wars memorabilia, playing the drums, and car racing. He also co-owned a nightclub called "Goldfingers" in Los Angeles, California.

Glenn Quinn died on December 3, 2002, aged 32. Police and autopsy reports revealed the cause of death to be a heroin overdose. Glenn's body was found on the couch of a friend he was visiting in North Hollywood, California.

During his time on Angel, he became extremely close to costars David Boreanaz and Christian Kane. The three were frequently spotted as guests at the Playboy Mansion. Later, during DVD commentary for the show's fifth season, both David and Christian recalled how much they still miss him.