Gunter Bresnik studied medicine for four years at the University of Vienna. He had begun doing coaching sessions while in school, and made contacts with top players. One of them was 19 year old Horst Skoff; in 1987 Skoff asked Bresnik to join him as coach during a five-week South American trip.

Bresnik had planned to take off only one semester; he coached Skoff for three years, and, with encouragement from his father, never returned to medical school.

In his coaching career since the mid-1980s, though never a tour level player himself, Bresnik has coached 27 top 100 tennis players, including Boris Becker from September 1992 to May 1993, Henri Leconte, Horst Skoff, Patrick McEnroe, Patrick Baur, Ernests Gulbis and Stefan Koubek.

Dominic Thiem, winner of the 2020 US Open, had been coached by Gunter Bresnik from age eight to 2019, but he has known Bresnik since he was three–after Thiem’s father, Wolfgang, came to work as a coach at Bresnik’s international tennis academy in Vienna in 1997.

In 2020-2021, Bresnik was working with Grand Slam semi-finalists Jerzy Janowicz and Ernests Gulbis. Since January 2021, he is also working with Gael Monfils.