Police spokeswoman Alicia Smiley said authorities received a call at about 5am on Sunday reporting a body found in a barn not far from where I'll Have Another, the horse that won Saturday's race, was stabled.
She said police had determined foul play was involved and were investigating the death as a homicide. The cause of death would be determined by the coroner, she said.
Chief Deputy Coroner Jo-Ann Farmer identified the victim as Adan Fabian Perez, 48, a stable worker from Guatemala.
An autopsy will be performed on Monday, she said.
I'll Have Another, ridden by jockey Mario Gutierrez, won the 138th running of the tradition-rich Kentucky Derby at Churchill Downs in a stunning finish before a record crowd of more than 165,000 people.