Made his US stage debut circa 1907 in New York's Yiddish theater, but did not appear in an English-language role until 1926. He would later alternate between 'Broadway' and 'Hollywood' for his roles, becoming one of the more distinguished actors in either venue. Failing eyesight and otherwise poor health forced him into retirement after his appearance in The Last Angry Man.
One of only six actors to receive an Academy Award nomination for Best Actor for his first screen appearance. (The other five actors are: Orson Welles, Lawrence Tibbett, Alan Arkin, James Dean and Montgomery Clift) Wife Bella was niece of actor Boris Thomashefsky. Interred at Hollywood Memorial Cemetery (now called Hollywood Forever), Hollywood, California, USA. Suffered all his life from a rheumatic heart. Received Oscar nominations for his his first and last ever screen performances ('The Valiant', 1929 and 'The Last Angry Man', 1959). Was unfortunately nicknamed 'The New Lon Chaney' at the start of his film career. Wife Bella was cousin of classical conductor Michael Tilson Thomas. During his live TV appearance in "The Last Clear Chance" in 1958, he appeared to be wearing a hearing aid. He was not. At his advanced age, and given the state of his health, it was no longer possible for him to memorize long stretches of dialogue on short notice. What he was wearing was a small radio transmitter, through which he was fed his lines just prior to speaking them. Turned down the role of Roy Earle in High Sierra, which was eventually given to Humphrey Bogart. A medium-sized man, he wore small lifts (adding about 3 or 4 inches) and padding to appear more hulking and ape-like as Tony in the original "Scarface." At the time that he left Warner Brothers, he was trying to convince the studio to let him star in a biography of Ludwig van Beethoven. Warners was not interested, and Muni never did portray the composer. If the film had been made, it would have been the first screen biography of Beethoven in English. Perhaps the most famous portrayer of Louis Pasteur, Muni was born only six days before Pasteur's death. Won Broadway's 1956 Tony Award as Best Actor (Dramatic) for "Inherit the Wind." The first actor to win an Academy Award for portraying a real-life person (The Story of Louis Pasteur) Of the six actors to receive an Academy Award nomination for "Best Actor" for their first screen appearance, he's the only one to eventually win an "Best Actor"-Oscar during his career.