Coulon began his boxing career in 1905. He won the American bantamweight title in 1908 and in a March 6, 1910, match for the vacated world bantamweight championship knocked out Jim Kendrick in the 19th round. Coulon successfully defended his title three times and held the championship until June 9, 1914, when he was knocked out by Kid Williams in the third round. He continued boxing until early in 1920 but interrupted his career to spend 1918 and 1919 in the U.S. Army as a boxing instructor.

In addition to being a world champion, Coulon is remembered for another noteworthy feat, winning two 20-round title matches within a span of 15 days. He defeated Frankie Conley on February 3, 1912, in Vernon, California, and Frankie Burns on February 18 in New Orleans, Louisiana. After retiring, Coulon performed in vaudeville and refereed amateur matches. Later he and his wife, Marie, opened a gymnasium on Chicago's south side, where many outstanding amateur and professional boxers trained. Coulon was inducted into Ring magazine's Boxing Hall of Fame in 1965.