Michael Peter Balzary (Flea) was born on 16 October 1962 in the Melbourne suburb of Burwood, Victoria. He is of Hungarian and Irish descent. His father, Mick Balzary, an avid fisherman, often took him fishing. When Flea was five, his family moved to Larchmont, New York for his father's career. In 1971, his parents divorced and his father returned to Australia. Flea and his siblings stayed with their mother Patricia, who soon remarried to a jazz musician. Patricia died in June 2013.

          Flea's stepfather, Walter Abdul Urban (1941–2011), frequently invited musicians to his house, where jam sessions would often take place. The family moved again to Los Angeles, California, where Flea became fascinated with his trumpet. He had no interest in rock music at the time; he idolized jazz musicians like Miles Davis, Louis Armstrong and Dizzy Gillespie. His stepfather was an "aggressive alcoholic", who eventually became involved in shoot-outs with police. "I was raised in a very violent, alcoholic household", Flea later said, "I grew up being terrified of my parents, particularly my father figures. It caused me a lot of trouble later in life". To cope, Flea began smoking cannabis at 13, and became a daily user.