In his first NFL season, Leemans played at the fullback position for the Giants and led the NFL with 830 rushing yards and an average of 69.2 rushing yards per game. He also impressed with his defensive play at the safety position. He was the only rookie to be honored by the NFL as a first-team player on the 1936 All-Pro Team. After the season ended, Leemans reported that he found it easier to make long gains in the NFL rather than college, crediting better blocking in the professional ranks.