From a Cajun family, Desormeaux grew up in a rural farming area located a few miles outside Maurice, Louisiana and attended North Vermilion High School.

"[2] Desormeaux was sixteen years old when he began working as an apprentice jockey at the Evangeline Downs racetrack in Lafayette, Louisiana.

He won his first career stakes race on December 13 of that year, riding Godbey in the Maryland City Handicap at Laurel Park Racecourse.

"[6] His success led him to move north to compete on the Maryland racing circuit, where his winning record earned him the Eclipse Award for Outstanding Apprentice Jockey in 1987.

His earnings were less affected, totaling $7.1 million in 1990, a 22% decrease from the year before,[1] a result of the higher purses generally available in California.

In 1992, Desormeaux became the regular rider of Best Pal, who put together a string of four graded stakes wins, including the Santa Anita Handicap.

"[6] On December 11, 1992, at Hollywood Park, Desormeaux was thrown when the horse he was riding, Judge Hammer, shied during the stretch drive.

He was then kicked in the head by a trailing horse, resulting in multiple skull fractures and a permanent hearing deficit.

[11][12][13] Prior to the fall, Desormeaux had been on pace to break José A. Santos' then-current earnings record of $14.8 million.

[1] Although he had a great deal of success early in his career, it wasn't until 1998 that he made an impact on the Triple Crown trail.

"To win the Kentucky Derby -- after having been on top of the world and then falling off the face of the Earth—it was like I was wide-awake inside my most fantastic dream.

However, Desormeaux lost his bid to win the Triple Crown when Victory Gallop beat Real Quiet by a nose in the final stride in the Belmont Stakes.

[23] In 2002, Desormeaux had a good year, ranked tenth by total earnings,[1] capped by his second win in the Santa Anita Handicap on Milwaukee Brew.

[26] Although he had no grade 1 wins that year, he did guide Zenno Rob Roy to third place in both the Takarazuka Kinen[27] and Japan Cup.

Two weeks later, Desormeaux rode Big Brown to victory in the Preakness Stakes at Pimlico Race Course, this time winning by just over five lengths while in hand.

Desormeaux received a good deal of criticism for his ride, though some praised him for protecting the colt from potential injury.

In 2010, Desormeaux teamed up with the filly Unrivaled Belle to score an upset win over Rachel Alexandra in the La Troienne Stakes.

[1] In the summer of 2014, Keith Desormeaux helped bring Kent back into the limelight by offering the ride on a promising colt named Texas Red.

When he finally did get his second chance at American Pharoah in the Travers Stakes, they both lost to Keen Ice, a colt that had previously been Desormeaux's mount.

Desormeaux credited his early years riding the Maryland circuit with giving him a crucial edge at Pimlico: "With these turns you want to paint the fence.

"[39] With the encouragement of his wife and brother, on May 31, 2016, he checked himself into an alcohol rehabilitation program at Cirque Lodge in Sundance, Utah.

After a stay of eight days, he flew to New York to prepare for the 2016 Belmont Stakes, accompanied by a coach who assisted him in maintaining sobriety.

[41] Kent's brother, Keith, did not blame the jockey, but noted the horse had run all three legs of the Triple Crown series and had struggled with the Belmont track.

[42] Desormeaux reached a milestone only 18 others in North America have met on Jan. 27, 2019 at Santa Anita Park, when he rode X S Gold to victory to secure his 6,000th win.