The state highway runs 30.00 miles (48.28 km) from U.S. Route 1 and US 17 Business in Falmouth east to SR 205 in Tetotum.

SR 218 begins in Falmouth at the intersection with US 1 (Jefferson Davis Highway) and US 17 Business, which joins US 1 south to cross the Rappahannock River into Fredericksburg and heads west as Warrenton Road to reconnect with US 17 at Interstate 95.

East of the railroad crossing, the state highway reduces to a two-lane undivided highway that connects residential subdivisions and several small communities east of Fredericksburg, including Sullivan, McCarthys Corner, and White Oak, which contains White Oak Church.

After passing through the hamlet of Passapatanzy, the state highway follows a curvilinear alignment through a forested area.

The state highway curves to the east to cross Upper Machodoc Creek, then turns south onto Tetotum Road.