Earlier this month, the 3-year-old colt became the 13th horse to win the Triple Crown, but just the second to do so while undefeated.
Jockey Mike Smith and trainer Bob Baffert were also on hand to sign autographs.
Justify's victory represents the second time in four years that a Santa Anita-based horse has won the three races that make up the Triple crown -- the Kentucky Derby, Preakness and Belmont Stakes.
American Pharoah accomplished the feat in 2015.