Michelle was born nine weeks premature in Phoenix, Arizona on July 2, 1983, and was named after the Beatles' song "Michelle". Though the surname Branch is French, her father is of Irish ancestry while her mother was born in the Netherlands; her maternal grandmother was a Dutch Indonesian and was held by the Japanese in an internment camp during World War II, while her maternal grandfather was French and Indonesian. She has an older half-brother, David, and a younger sister, Nicole.

Branch started taking voice lessons at a local university when she was 8 years old. She received a guitar for her fourteenth birthday from her uncle. She locked herself in her room and taught herself chords; within a few days she had composed her first song. She focused on the arts during high school, and was writing songs extensively. She attended Sedona Red Rock High School in Sedona but with the support of her parents, decided to continue her high school education through home schooling, which a