The highway runs 2.32 miles (3.73 km) from the Rhode Island state line east to U.S. Route 1 (US 1) within North Attleborough in western Bristol County.

Route 120 connects North Attleborough with Cumberland, Rhode Island.

Route 120 begins at the Rhode Island state line in the town of North Attleborough.

The highway continues west as Rhode Island Route 120 into the town of Cumberland.

The route heads east as two-lane Hickory Road, which crosses the Sevenmile River.