Hart turned pro in 1990 and joined the PGA Tour in 1991. His first win came in 1996 at the rain-shortened Bell Canadian Open, his 160th PGA Tour start. His second win was at the 2000 Honda Classic. Hart also finished in a three-way tie for first in the 2004 EDS Byron Nelson Championship, which he and Robert Damron lost in a playoff to Sergio García.
Although Hart has only won two PGA tournaments, he was one of the most consistent players on the Tour. From 1991 to 2009, Hart had 55 top-10 finishes, including four runner-up finishes. His best finish in a major was sixth-place tie at the 1993 PGA Championship.