It is a minor connecting route, running 10.3 miles (16.6 km) from an intersection with SR 191 near East Machias to an intersection with U.S. Route 1 (US 1) in Dennysville.

SR 86 runs mostly through unincorporated forest land.

SR 86 begins at an intersection with SR 191 in Marion Township, part of the unorganized territory of East Central Washington, just outside East Machias.

SR 86 proceeds eastward through unincorporated Edmunds Township into the town of Dennysville, where it ends at US 1.

SR 86 is named King Street in Dennysville.