It is a Grade I stakes race for three-year-old Thoroughbreds at a distance of 1+1⁄4 miles (2.0 km), and has been run at Churchill Downs racetrack since its inception in 1875.

[1] The Kentucky Derby is only open to three-year-old Thoroughbreds,[9] thus all entrants in the 2018 race were part of the 2015 North American live foal crop of roughly 22,000.

[10] The field was limited to twenty horses who qualified based on points earned in the 2018 Road to the Kentucky Derby, a series of designated races that was first introduced in 2013.

Good Magic, the champion two-year-old from 2017, finished second in the series by winning both the Breeders' Cup Juvenile and the Blue Grass Stakes.

"[15] Trainer Todd Pletcher, who won the 2017 Kentucky Derby with Always Dreaming, had four of the leading contenders: Magnum Moon, Audible, Vino Rosso, and Noble Indy.

Magnum Moon was ranked number two on the National Thoroughbred Racing Association top three-year-old poll of April 16 after his win in the Arkansas Derby.

However, O'Brien felt that the colt would be equally suited to racing on the dirt given his pedigree: Mendelssohn is a half brother to multiple Eclipse Award-winner Beholder.

[20][21] Because the Derby was held on a rainy day, the surface of the track was sealed to mitigate the effect of heavy rain on the footing.

[24] On the track, Justify's jockey Mike Smith used the colt's early speed to gain vantage position near the rail moving into the first turn.

[25] In the final turn, Bolt d'Oro and later Good Magic were both put to a drive, while Promises Fulfilled began to drop back.

On the other hand, Instilled Regard, who broke from post position 15 and was also involved in the initial bumping incident, rallied from 17th place to finish fourth.