Labyorteaux is the adopted son of Ronald Labyorteaux (1930–1992), an interior designer and talent agent, and Actress Frances Marshall (1927–2012). He is brother of actor Matthew Laborteaux and Actress Jane Laborteaux. Patrick was adopted at a young age after being labeled "unadoptable". Early in his career he was billed under the name Patrick Laborteaux, dropping the "y".
He starred on television and in film; his well-known TV roles are on the hit NBC series Little House on the Prairie as Andrew "Andy" Garvey from 1977–81, and on the CBS hit series JAG as Lt. Cmdr. Bud Roberts from 1995 to 2005, a role he reprised in three episodes of JAG's spin-off, NCIS. Other TV shows on which he has made guest appearances include Starsky & Hutch, 21 Jump Street, Living Single, Yes, Dear, Lois & Clark: The New Adventures of Superman, The Love Boat, Ghost Whisperer, and iCarly.
He starred in films as well: one of his well-known roles is in the 1987 comedy film Summer School as football player Kevin Winchester alongside Future JAG/NCIS costar Mark Harmon. He appeared in the 1989 cult film Heathers as Ram Sweeney. He voices cartoons such as Spider-Man: The Animated Series, Godzilla: The Series and others.