SR 338 begins at an intersection with US 29 and SR 237 (Washington Street) in the independent city of Falls Church.

There is no access from southbound US 29 to eastbound SR 338; that movement is made via Annandale Road at the intersection immediately to the east of the terminus.

SR 338 heads east as a two-lane undivided street through a residential area.

Shortly after leaving Falls Church and entering Fairfax County, the state highway reaches its eastern terminus at a seven-way junction with US 50 (Arlington Boulevard), SR 7 (Leesburg Pike), and SR 613, which heads north as Wilson Boulevard and south as Sleepy Hollow Road.

The mass of intersections allows access to westbound SR 7 back toward Falls Church.