Hans Muller was a member of De Dolfijn swimming club in Amsterdam and played later for AZ&PC in Amersfoort. Muller was a member of the Dutch Olympic water polo team at both Roma in 1960 and Tokyo in 1964. In 1972, he was team manager for the Dutch water polo team at the München Olympics. After his career as a water polo player, he became director/owner of a dress store, which was for many years the supplier of the clothing for the Dutch Olympic teams. Muller was on the board of the Netherlands Olympic Committee from May 1985 to May 1989.