Naish grew up in a tough section of New York and at 16 enlisted in the Navy. He served with the Army Signal Corps during World War One; at war's end he remained in Europe, traveling about and learning several langauges. He returned to the U.S. aboard a ship that dropped him off in California and journeyed to Hollywood to find work as an extra and stunt man. In 1926 he became an understudy with the road company of The Shanghai Gesture and accompanied the show to Broadway. After acting in a couple of Broadway plays he returned to Hollywood in 1930 and began getting roles as a featured player. Soon he was much in demand as a highly versatile character actor; a master of dialects, he specialized in playing almost any ethnic type, and during his career he portrayed Italians and other Latins, Germans, Chinese, Japanese, Jews, Arabs, and Indians. Oddly, although he was Irish, his dark complexion prevented him from playing Irishmen in any of his films. He was twice nominated for a Best Supporting Actor Oscar, first for playing an Italian in Sahara (1943), then for playing a Mexican-American in A Medal for Benny (1945). He remained busy as a screen actor through the mid '50s, after which he appeared in only a few more films. He starred as an Italian in the radio comedy series Life with Luigi, then in the '50s appeared in the TV version of that series. He later starred in the title role of the TV series The New Adventures of Charlie Chan and costarred in Guestward Ho!