Mandella's father, a blacksmith, introduced him to horses at an early age and while still in high school he began starting and training horses at a nearby ranch. He spent a year in New York as assistant to Lefty Nickerson and then took a job with Texas horseman Roger Braugh in 1974.
Two years later, Richard Mandella returned to California and opened his own stable. His wins began almost immediately with Bad 'n Big and continued with Phone Trick, Dare and Go, and Pleasantly Perfect. Between 1996 and 1998 Mandella won six straight million dollar races in Southern California with Dare and Go, Siphon, Gentlemen and Malek. Mandella has seen six of his horses run in the Kentucky Derby.
In 2006 Mandella wrote the introduction to Santa Anita Morning Rhapsody, by photographer-author Karen S. Davis, a book documenting morning thoroughbred racetrack training. "Most people who enjoy racing don't realize how special these early hours are, watching ... the relationship between horse and man," he wrote.
Richard Mandella lives in Bradbury, California with his wife Randi, son Gary (also a trainer) and daughter Andrea.