Perhaps Tunney's most famous moment as a boxer came as a result of something that happened to him, not his adversary: Fight number 2 with Dempsey, on September 26 of 1927, at Philadelphia, became known as The Long Count Fight. During round seven, Tunney was caught against the ropes and hit by a Dempsey combination, and he fell to the canvas, on a sitting position. Dempsey did not know that a new rule, stating that the standing boxer had to go to a neutral corner after a knockdown, had been created recently, so he refused to walk to a neutral corner. The referee did not begin to count until after Dempsey finally obeyed his commands, and Tunney was able to get up at the count of nine. Some estimates put Tunney's time laying on the floor as 16 seconds, but a clock set on the fight's footage has shown that he stayed there for 13 seconds. Had Dempsey known of the new rule, he would have likely won by knockout. Tunney dropped Dempsey in round eight, and went on to win a unanimous decision.
Tunney, who was a U.S. Marine, was not undefeated as a boxer: He lost a 15 round decision to Harry Greb for the American Light Heavyweight title, defeat which he later avenged. As a Heavyweight, however, he was never defeated.
Tunney also had an acting career, participating in one movie.
He was elected as Ring Magazine's Fighter of the Year in 1928. He was elected to the World Boxing Hall of Fame in 1980. He was elected to the International Boxing Hall of Fame in 1990. He was elected to the Marine Corps Sports Hall of Fame in 2001.