Claës König was a professional officer and became a lieutenant in the King’s Own Mounted Regiment in 1913, and was later promoted to captain in 1921. He was transferred to the reserves in 1935 becoming Equerry of the Royal Mews. In 1920 he won a gold medal in team jumping with the Swedish team. Four years later in Paris he won another silver medal in team eventing, finishing fifth in the individual competition, again as the best Swede.
König was also active in organizing equestrian sports. He was a teacher at the riding school in Strömsholm, and later held positions as the treasurer of the Jockey Club and secretary and chairman of the executive committee of the Swedish Equestrian Union. In 1936 he was one of the leaders of the Swedish equestrian team at the Berlin Olympics.