At the start of his three-year-old campaign, Sea Hero was winless in his first three starts. His best result was a fourth-place finish in the Blue Grass Stakes to Prairie Bayou, who then became the lukewarm favorite for the Kentucky Derby. Sea Hero entered the Derby as a 13-1 longshot and pulled off the upset by lengths over Prairie Bayou. It marked the first Derby win for jockey Jerry Bailey and for 71-year-old trainer Miller. It was also the first Derby win for Mellon, who became the only person to ever win the Kentucky Derby, The Derby, and the Prix de l'Arc de Triomphe, having captured the latter two with Mill Reef in 1971.