Stephan Waser enjoyed a successful career on the international bobsledding scene in the years following World War II. Representing Switzerland, he first gained international attention at the 1947 World Championships by winning the two-man event with veteran Fritz Feierabend. He was not selected for the 1948 Winter Olympics, but teamed up with Feierabend at the 1950 World Championships and captured gold in the two-man and silver in the four-man, the latter with the assistance of Albert Madörin and the non-Olympian Romi Spada. Waser and Feierabend then attended the 1952 Winter Olympics, where they earned bronze in the two and four-man events, the latter alongside Madörin and André Filippini. Waser retired from active competition shortly after the Games.