Diedrich was born on December 24, 1966 in Alexandria, Virginia. He first got the urge to perform while he and his family were living in Paris, France. He moved back to the United States to attend high school, and then went to college at the North Carolina School of the Arts.
Diedrich later moved to Los Angeles, California and began auditioning for acting roles. He landed guest roles on Star Trek: The Next Generation, The Fresh Prince of Bel-Air, Cheers , and Quantum Leap. Diedrich is perhaps best known for his role on The Drew Carey Show as Oswald. He currently resides in Los Angeles with his family.