Harry was adopted when she was three months old by a family from Hawthorne, New Jersey, and attended Hawthorne High School, where she graduated in 1963. Prior to starting her singing career she moved to New York in the late 1960s and worked as a secretary at the BBC Radio New York office for one year. Later, she was a waitress at Max's Kansas City, and worked in a Dunkin' Donuts, after which she was a dancer in Union City, and a Playboy Bunny.

She began her musical career with a folk rock group, the Wind in the Willows. Harry then joined a girl-group trio, The Stilettos, in the early 1970s. The Stilettos' backup band included her eventual boyfriend and Blondie guitarist, Chris Stein. Harry and Stein formed the band Blondie in the mid-1970s, naming it for the wolf whistle men often yelled at Harry from passing cars. Blondie quickly became regulars at Max's Kansas City and CBGB's in New York City. After a debut album in 1976, commercial success followed in the late 1970s and ea