SR 129 begins just northwest of Fort Stewart, in rural Evans County, at an intersection with Old Hwy.

The highway then heads northwest to an intersection with US 280/SR 30 (West Main Street) in Claxton, still within Evans County.

SR 129 continues to the northwest and then curves to the north-northeast for just over 2 miles (3.2 km), crossing over the Canoochee River along the way.

During this stretch, it crosses over, but does not have an interchange with, Interstate 16 (Jim Gillis Historic Savannah Parkway).

It continues to the north until it meets its northern terminus, an intersection with SR 46 (East Broad Street).