Heinrich Keller first swam competitively for SC Horgen in the late 1930s, and was a top player on its water polo team throughout the 1940s. He joined the SC Zürich team in 1948, and soon became one of their best players, resulting in his selection for the Swiss Olympic water polo team to compete at the London Olympics. Keller continued to play for SC Zürich until 1952 before later returning to his first club, SC Horgen by 1955.