Came to Manhattan College on a baseball scholarship and became lethal both on the mound and with his bat. Right from the start, it was evident that he would be an exciting pitcher to watch with a 10-0 shutout to his credit freshman year against now archrival St. John's. Shutouts became a habit for the right-hander under Hall of Fame coach Dave Curran. He rarely gave up a run, boasting an ERA of 1.35 during his sophomore year, while batting a solid .321. His honors in Riverdale included: All Star Team of the Metropolitan Collegiate Baseball Conference in 1959, Manhattan's Most Valuable Player Award and leading pitcher in the Met Conference in 1960 and honorable mention as a leading pitcher in the Met Conference in 1961. Recruited professionally throughout college, Leder decided to earn his degree first. He signed with the Cincinnati Reds upon graduation, pitching for manager Johnny Vandeer Meer's Tampa team. Tom continued to pitch shutouts at the professional level with an 1.60 ERA and a 6-1 record, earning a spot on the 1962 roster before an injury ended his baseball career.

Although baseball was considered Leder's strength, he managed to put up good numbers on the hardwood throughout his basketball career. Captain of the team in 1960-61, Leder shot over 50% from the field throughout his career and averaged more than six rebounds per game. One of the highlights was a 32-point game over St. John's as a freshman. Regularly scoring in double figures, Leder was a key to victory, especially when it came to archrivals. The Jaspers beat Fordham all three seasons Leder played. He also scored 19 points against Providence in the NIT in 1959.