James Stewart (Jefferson Smith), Jean Arthur (Clarissa Saunders), Claude Rains (Joseph Harrison Paine), Edward Arnold (Jim Taylor), Guy Kibbee (le gouverneur Hubert Hopper), Thomas Mitchell (Diz Moore), Eugene Pallette (Chick McGann), Beulah Bondi (Ma Smith), HB Warner (Senate Majority Leader), Harry Carey (le président du Sénat), Astrid Allwyn (Susan Paine), Ruth Donnelly (madame Hopper), H.B. Warner (Senate Majority Leader - Agnew), Grant Mitchell (Senator MacPherson), Porter Hall (Senator Martin Monroe), H.V. Kaltenborn (er selbst - Radiosprecher und Erzähler), Charles Lane (Nosey), Pierre Watkin (Minderheitsführer Barnes), William Demarest (Carl Griffith), Dick Elliott (Bill Cook), Billy Watson (Peter Hopper), Delmar Watson (Jimmie Hopper), John Russell (Otis Hopper), Harry Watson (Hopper-Junge), Garry Watson (Hopper-Junge), Larry Simms (Hopper-Junge), Erville Alderson (Graphologe), Harry Anderson (Ganove), Stanley Andrews (Senator Hodges), William Arnold (Reporter), Sam Ash (Senator Lancaster), Edwin August (Senator), Frank Austin (Erfinder an Smiths Bürotür), Harry A. Bailey (Senator Hammett), Tommy Baker (Pfadfinder), Kathryn Bates (Frau vom Komitee), Brooks Benedict (Senatsangestellter), Wilson Benge (Hoppers Butler), Wade Boteler (Familienvater), Harry C. Bradley (Arthur Kim), Lynton Brent (Fotograf)