It proceeds east to Bartlett and intersects US 70/US 79/US 64/SR 1, where it becomes the unsigned companion route of US 64 and becomes a primary highway.

They then go east and pass just north of Lenow before having an interchange with I-269 (Winfield Dunn Parkway/Memphis Outer Beltway) (Exit 15), in Eads.

Not even a half mile away, they intersect with SR 205 before crossing into Fayette County.

They then enter Whiteville, where US 64 Bus begins and goes east through downtown while US 64/SR 15 follow a new bypass to the south.

US 64/SR 15 then intersect and have a short concurrency with SR 224 just north of Stantonville before entering Adamsville.

US 64/SR 15 then go through a narrow valley before entering Waynesboro, bypassing the city to the west and north.

They then enter some farmland and have an interchange with the Natchez Trace Parkway just before crossing into Lawrence County.

They then come back around to meet the other end of US 64 Bus before leaving Lawrenceburg and continuing east through more mountains.

It then passes through Bodenham before intersecting and becoming concurrent with SR 166 and entering Pulaski.

They continue east through farmland and mountains to cross the Elk River before passing through Kelso.

They then intersect and have a short concurrency with SR 121 before entering Franklin County.

They go east to Saint Andrews where they intersect SR 156 before crossing into Marion County.

They then enter Monteagle and SR 15 ends at an intersection with US 41/SR 2 just west of downtown.