Inspired by his father, he then started an acting career, appearing in summer stock theatre and in small television roles.

In 1978, he appeared as Barlow, a young surfer, in the John Milius drama film Big Wednesday opposite Jan-Michael Vincent and Gary Busey.

Katt explained in a 1979 interview with critic Roger Ebert that he was holding out only for parts that were personally interesting to him.

He was seriously considered for the role, which went to Mark Hamill, and Katt instead starred that year in First Love, playing a college student who experiences his first romantic relationship.

In 1981, Katt was cast as the title role in a filmed version of the Broadway musical comedy Pippin, which received mixed reviews.

In recent years, he has returned to genre work, with appearances in Andromeda and Justice League and roles in the award-winning film Gamers (2006), The Man from Earth (2007), and Alien vs Hunter (2007).

Katt briefly appeared in Heroes season 3 in "The Butterfly Effect" as a nosy reporter investigating Ali Larter's character.

Katt also has written a Greatest American Hero comic book and contributed to that series' Facebook page.