Karel Wälzer was a goaltender whose career began in Bohemia with České Sportovni in 1910. He had a relatively short career, interrupted by World War I, retiring after the 1920-21 season. Wälzer minded the net for Bohemia at the 1912 and 1914 European Championships, winning a gold medal in 1914, and played for Czechoslovakia at the 1921 Europeans, winning a silver medal. Bohemia also won the 1912 Europeans but the tournament was annulled as Austria competed, which was not then a member of the Ligue Internationale de Hockey sur Glace (LIHG), the forerunner of the International Ice Hockey Federation (IIHF). At the 1920 Olympics, Wälzer injured his thumb early in practice but was able to play in the match for the bronze medal against Sweden, and shut them out, 1-0.