"I'm here because you're here because I feel the Bern," the 71-year-old Taxi and It's Always Sunny in Philadelphia star told the crowd of 2,300 at Affton High School.
DeVito – of famous short stature – first spoke virtually hidden behind the podium then retrieved a box to stand on, drawing laughs and cheers from the crowd.
DeVito went on to describe the Democrat presidential candidate as "a man who speaks the truth, a man who has got the knowledge, a man who has been there for us since the beginning of his career."
He also compared the 74-year-old Vermont senator to a wise and iconic Star Wars mentor.
"We need you Obi-Wan," DeVito told Sanders.