Gustafsson was a professional tennis player from 1985 to 2001. He won 14 singles titles in his career, including four at the Swedish Open in Båstad .
He reached his highest world ranking position in 1991 with 10th place. In 1994 he was in the quarter-finals of the Australian Open , this was his best performance in a Grand Slam tournament . In 1998 he won the Davis Cup with the Swedish team . Between 1991 and 1999 he was used in nine Davis Cup matches. He played 14 individual games in which he was able to celebrate ten wins.
Gustafsson was known for his consistency. Between November 9, 1987 and April 22, 2002 he was only eight months (between February and October 1995) not in the top 100 of the ATP world rankings .
He also played for several clubs in the German tennis Bundesliga , such as Bamberg and Essen.