Katt attended Orange Coast College before pursuing a career as a musician. Inspired by his father, he then started an acting career, appearing in summer stock theatre and in small television roles. His earliest film credits include the role of a jock, Tommy Ross in Brian De Palma's 1976 horror film adaptation Carrie, which allowed Katt to make a name for himself. In 1978, he appeared as Barlow, a young surfer, in the John Milius drama film Big Wednesday opposite Jan-Michael Vincent and Gary Busey. His mother in that film was his real-life mother, Barbara Hale. The following year he took the role of Sundance Kid in the 1979 film Butch and Sundance: The Early Days. The role in Big Wednesday made him so well known in the surfing community that in 2004 he presented one of the Association of Surfing Professionals awards at their annual World Championship Tour ceremony to wild applause from the crowd of professional surfers. Katt explained in a 1979 interview with critic Roger Ebert that he was holding out only for parts that were personally interesting to him.