Eddery takes over from the colt's regular jockey, Willie Ryan.
Trained by Henry Cecil and owned by Lord Howard de Walden, Sebastian was unraced as a juvenile but has won two of his three starts this year. Since a 10-length success at Salisbury two weeks ago, William Hill have cut his price for Epsom from their initial quote of 25-1 to a current 7-1.
Lord Howard de Walden's racing manager, Leslie Harrison, announcing that Eddery will ride Sebastian, expressed surprise that the colt's price was so short.
The colt's 82-year-old owner is seeking his second Derby win after the success of the Henry Cecil-trained Slip Anchor - a three-parts brother to Sebastian's dam - in 1985.
A 10-times champion jockey, Eddery won his first Derby on Grundy in 1975 and has since landed the race on Golden Fleece in 1982 and Quest for Fame in 1990.
Eddery secured two more Classic rides yesterday when he was booked for Asterita in the Oaks and Caramba in the French equivalent, the Prix de Diane at Chantilly. Both are trained by Richard Hannon.
Asterita earned her place at Epsom after a battling win in the Lingfield Oaks Trial and has been backed from 25-1 into 16-1 with Corals in anticipation of the news.
"She ran a good race at Lingfield and the 1,000 Guineas form is not standing up," Hannon said.
Caramba had chased home Pure Grain in the Musidora Stakes at York and had been supported at around 14-1 for Epsom. But she is now considered a better prospect over the two- furlong shorter trip of the Prix de Diane.Reuse content