Graduates from the Joanne Baron/D.W. Brown Studio in Malibu, California, were left stunned when the 'Mission: Impossible' star turned up unannounced at the ceremony and gave a rousing commencement speech filled with humorous stories from his career.
A source at the school told the New York Post newspaper: "It was one of the most inspiring speeches we've had. It was so much more than a lecture about what to do in an audition."
The 51-year-old star - whose cousin, William Mapother, is a graduate of the acting school - had students in fits of laughter as he recalled his own rocky start in Hollywood.
In one particular story, Tom explained how he was so "nervous" he'd be fired from 1981 film 'Taps' after shaving his head without the director's permission.
As well as entertaining the crowd with anecdotes, the movie icon offered more practical advice to the young upstarts, warning them not to become divas.
A source explained: "He said that when you do finally get the chance of being in a movie, don't spend your time in the trailer. He said you need to experience everything on the movie; talk to everyone on the crew - the grips, everyone. Learn everything you can. You will never get that time back.
"He talked about trying to be as prepared as possible, and that you can only depend on yourself."