Gustafson has been working as an actor since 1953. In 1957, he was hired for the Swedish royal theater Dramaten andalso began performing in television plays. His TV debubt was in 1955 in a small part in Hamlet. In Sweden, he is best known for the role of Dynamit-Harry from the Jönssonligan movies, a Swedish remake of the Danish Olsen Banden movies. Another role that he is known for in the Nordic countries are the role of Alfred in the TV series and movies about Emil i Lönneberga, based on stories written by Astrid Lindgren.
Gustfason's long film career also included a supporting role in Ingmar Bergman's Den goda viljan. His voice work include Alfons Åberg short movies, Pelle Svanslös and Disney's Robin Hood as Friar Tuck.