A hospital helicopter responded to the event amid hundreds of spectators.
Forty-year-old Robert Costello of Southernpines, North Carolina fell from his horse while attempting a jump in the cross-country course.
Organizers say Costello was life-flighted to the hospital as a precautionary measure.
"Our competitors wear very good safety helmets and chest protectors, and when they do sustain a fall, which really doesn't happen that often, we hope that the safety equipment lessens the severity of the injury," says Rusty Lowe, the Red Hills Horse Trials safety advisor.
Costello was taken to Tallahassee Memorial Hospital. Lowe says Costello has a minor head injury and no fractures and the horse also has no serious injuries.