Harrison appeared on an episode of M*A*S*H before garnering fame in 1979 with the role of surgeon Dr. George "Gonzo" Gates on Trapper John, M.D., starring opposite Pernell Roberts.

The medical drama was spun off from M*A*S*H.[3] Harrison remained as Gonzo on Trapper John until the middle of the show's seventh season, when he decided to leave for other ventures.

[citation needed] Harrison's later role as stripper John Phillips in the 1981 TV movie For Ladies Only made him a favorite with women and gay men in the 1980s.

[4] As Falcon Crest ended production in early 1990, the series' parent studio, Lorimar Television, cast Harrison in its upcoming CBS sitcom The Family Man, from producers Thomas L. Miller and Robert L. Boyett.

[citation needed] Harrison starred in the WB Network's Safe Harbor and One Tree Hill and has made guest appearances on other shows such as Touched by an Angel, Judging Amy, Rizzoli & Isles, Reunion, Joey, Law & Order: Special Victims Unit, Drop Dead Diva and Hot in Cleveland.

Harrison played Billy Flynn in a touring production of Chicago, and he was the male lead as Oliver Caldwell in each film of the Au Pair trilogy.