NY 120 begins at an intersection with US 1 (Boston Post Road) in the city of Rye. The route proceeds northward along Purchase Street as a two-lane street through the Locust Avenue Business District, intersecting a handful of local streets and serving Rye's station on the Metro-North Railroad's New Haven Line. Past the station, the highway passes under the New Haven Line, Amtrak's Northeast Corridor line, and I-95 in quick succession ahead of the Purchase Street Business District. The commercial surroundings give way to residential neighborhoods after three blocks as NY 120 winds northward through the northern part of Rye to the adjacent village/town of Harrison.