It travels through portions of Glascock and Warren counties.

Its routing is entirely northwest of Mitchell.

SR 123 begins in at an intersection with SR 102 in Mitchell, within Glascock County.

It heads northwest along local roads until it curves along the Glascock–Warren county line until branching north onto Shoals Road.

SR 123 heads north along Shoals Road for a few miles before meeting its northern terminus, an intersection with SR 16.