Matthew Broderick as Richard Feynman

Patricia Arquette as Arline Greenbaum

Peter Riegert as Mel Feynman

Jeffrey Force as Young Richard

David Drew Gallagher as Harold

Raffi Di Blasio as Robert

Josh Keaton as David

James Hong as Abacus Adder

Melissa DeLizia as Young Joan

Peter Michael Goetz as Dr. Gell-Mann

Kelly Wolf as Nurse Kate

Mary Pat Gleason as County Nurse #2

Joyce Van Patten as Aunt Ruth

James Le Gros as John Wheeler

Zeljko Ivanek as Bill Price

Joshua Malina as Calculator Kid #3

Matt Mulhern as Gate Guard