Stith attended St. Francis Preparatory School in Brooklyn and committed to St. Bonaventure University, where he and older brother Sam formed a formidable 1-2 punch. The Stith brothers posted a 52.0 points per game combined scoring average for the 1959-1960 season. Tom Stith became St. Bonaventure's first consensus All-American in 1960 and 1961. Stith left St. Bonaventure as the school's all-time leading scorer, ending his career with 2,052 points. Stith finished second in the nation in scoring to Oscar Robertson in 1960, averaging 31.5 points per game, and he then finished third in 1961 with 29.6 points per game.
After completing his collegiate eligibility, Stith was selected by the New York Knicks as the second pick overall in the 1961 NBA Draft, behind Indiana'sWalt Bellamy. He made the team and played in 46 games over the 1961–62 seasons. However, Stith contracted tuberculosis only a month into the season, and his NBA career was cut short at 25 games and 3.2 points per game.