Nicholson was born and raised in Medford, Massachusetts (outside Boston), the eldest of Kate (née Gilday) and James O. Nicholson Jr.'s four children.
After graduating from Arlington Catholic High School, she modeled in New York for six months, quit for a year, then resumed her modeling career in Paris for another six months. After returning to New York, she attended Hunter College as a general studies major for two years. While in New York, Nicholson supported herself by waitressing and eventually left school to study acting and begin her professional career.
