Born in Gaffney, South Carolina, Montgomery was initially a basketball and American football player, before trying out at athletics. Montgomery did not qualify for the 1996 Summer Olympics 100 m, although he did compete in Atlanta in the heats of the 4 x 100 m relay team that eventually finished second. He qualified for his first major international tournament in 1997, and won the bronze medal at those World Championships, finishing third behind Maurice Greene. Two years later, he came sixth in the individual final, but won the gold medal with the US relay team.
Montgomery did not qualify for the individual event of the 2000 Summer Olympics, though he again ran as an alternate in the heats of the relay event; in the final, the USA won the gold medal.
The greatest moment in Montgomery's career came in September 2002, as he broke Greene's 100 m World Record by 0.01. With a tailwind of 2.0 m/s (the maximum allowed), Montgomery ran 9.78 to earn the title "fastest man on earth".