Katz was born Meyer Myron Katz on Sawtell Court in Cleveland, Ohio, the son of Johanna (née Herzberg) and Menachem Katz. Originally one of five children, Mickey lost an older sister to diphtheria when he was about four years old.^[1] Menachem supported the family as a tailor, but money was always tight in the Katz family. As children Mickey and his siblings contributed to the family finances by entering amateur musical contests in the neighborhood theaters and bringing the prize money home to their parents.^[1] Even after graduating from high school, Mickey continued to support his family with the money he earned from his music.

Out of high school, Katz was hired by Phil Spitalny to go on a road tour. While waiting at the train station to leave, Katz met Grace Epstein, his future wife. He was seventeen and she was fourteen.^[1] He married her three years later, in 1930. They had two sons, Joel Grey and Ronald.^[2][3] Each of Katz’s sons had two children. Joel fathered Jennifer Grey and Jim Grey, and Ronald fathered Randy Katz and Todd Katz. In 1977 Katz told the story of his life in a biography called Papa, Play for Me.^[1]