SR 124 begins at an intersection with I-20/US 278/SR 12 in Lithonia, in DeKalb County.

Through Snellville north to Lawrenceville, the road is known as Scenic Highway.

[2] In town, it intersects US 78/SR 10 and then, the Ronald Reagan Parkway; the Eastside Medical Center, Snellville's largest employer, is located on this portion of the route.

Northwest of Dacula, it meets SR 324, passes by Mill Creek High School a couple miles later, and crosses into Barrow County shortly thereafter.

The road heads westerly until it meets its northeastern terminus, an intersection with SR 11 in the southwestern part of Jefferson.