The state highway runs 11.19 miles (18.01 km) from SR 143 in Newport News east to a dead end at the Back River in Poquoson.

The state highway intersects SR 600 (Big Bethel Road) and passes through a forested area before and after crossing the western city limit of Poquoson.

East of the center of the city, the state highway veers onto Poquoson Avenue, a curvy road that gradually turns south.

SR 171 turns east onto Messick Road, which veers south through marshland west of Plum Tree Island National Wildlife Refuge.

The state highway reaches its eastern terminus at a boat yard at Messick Point on the Back River, which separates Poquoson from Hampton.