Julio Müller started playing polo in 1924 at the age of 19 and went on to play for two of the country’s top teams Roehampton and La Laguna. In 1926, he was selected for the Mexican national team in a tournament in Texas and in 1927 and 1928 he played in Europe, mostly in England and France, and was a regular member of the Roehampton and Chapultepec teams. The latter was a newly formed team by fellow Mexican Archibaldo Burns. Müller was the only civilian selected for the 1936 Mexican Olympic polo team and played at number three as they won the bronze medal. Mülller later became the secretary of the Mexican Polo Association, and his son, Julio Jr., was also a polo player and won the US Open in 1961 and 1964.