Jonathan Taylor Thomas Thomas was born in Bethlehem, Pennsylvania to Stephen Weiss and Claudine Taylor, who divorced in 1991; he has Jewish and Portuguese ancestry. He has a brother, Joel Thomas Weiss, whose middle name he adopted as his pseudonym, in to avoid confusion with an existing actor named Jonathan Weiss.
In 1986, Thomas moved with his family to Sacramento, California, and was cast in a Burger King commercial at the age of eight.
As a child, Thomas played Randy Taylor on the popular television show Home Improvement. He went on to voice Young Simba in Disney's The Lion King and Pinocchio in The Adventures of Pinocchio. He remained with Home Improvement well into his teenage years, being written out of the show in 1998 to accommodate his film career. He served as guest timekeeper at WrestleMania XI in 1995.
As Thomas got older, he earned a reputation as a teen heartthrob and was a leading cover boy on teen magazines. In 1998, he starred in the Christmas comedy I'll Be Home for Christmas, which, although heavily hyped as his break into movies, was actually a commercial flop. He also appeared in the movies Man of the House, Tom and Huck, Wild America, Common Ground and Speedway Junky. He had a guest role on the ABC sitcom 8 Simple Rules for Dating My Teenage Daughter in early 2004, and appeared in the WB's Smallville in 2003 and 2004. In 2005, he had a guest role in UPN's high school detective drama Veronica Mars.
In 2006, he appeared as young Simba (via stock audio from Lion King) in the PlayStation 2 video game Kingdom Hearts II, developed by Square-Enix.
Thomas attended Harvard University and the University of St. Andrews in Scotland as a visiting student. He is also a vocal opponent of abortion, and has been very active in various pro-life activities and causes.