Prior to the completion of sections of Interstate 22 (I-22), SR 118 served only as the unsigned partner route of U.S. Route 278 (US 278) between the Mississippi state line, west-southwest of Sulligent, and Guin.

The current eastern terminus of the highway is in the western part of Jasper, at an intersection with SR 69.

At Carbon Hill, the highway briefly expands to four lanes, only to revert to a two-lane road as it heads southeasterly towards Jasper.

SR 118 starts at US 278 at the Mississippi state line, intersecting US 43/SR 171.

It has an interchange with I-22/US 78/SR 4 east of Carbon Hill and again west of Jasper before it ends at SR 69.