Though it runs in generally in an east–west direction, the route is signed north–south.

SR 203 begins at an intersection with SR 3 (Historyland Highway) at Lyells on the northern edge of Richmond County.

The state highway heads east as Oldhams Road and enters Westmoreland County.

SR 203 passes through Threeway and Oldhams before meeting SR 202 (Cople Highway) at Grays Corner.

The two highways run concurrently southeast on Cople Highway before SR 203 splits to the northeast as Kinsale Road.