Castellano grew up in a racing family in Venezuela. His father and uncle were jockeys and his brother, Abel Jr., is based in South Florida. He began riding in 1996, moved to the U.S. in 1997 to pursue his career and relocated to the higher-profile New York circuit in 2001. Castellano won the Breeders' Cup Classic on Ghostzapper in 2004 and picked up his first victory in a Triple Crown race on Bernardini in the 2006 Preakness. In 2010 at Saratoga, he won five consecutive races on the third day of the season and captured the meet's biggest prize with a victory in the Travers on Afleet Express. He led the Saratoga jockeys in purse money earned in 2011 with victories in five Grade 1 stakes: the Ruffian, the Personal Ensign, the Ballerina, the Travers and the Diana. He also won the Grade 1 Just a Game, Maker's Mark, Ashland and Prioress and finished the season with a career-best $15,677,027 in purse earnings.
Normandy Invasion, a Chad Brown trainee, will be the 2013 mount for Castellano in the Kentucky Derby. Castellano piloted the colt to runner up efforts in both the Wood Memorial (G1) behind Verrazano and Remsen Stakes (G2) to Overanalyze.