The 48.51-mile-long (78.07 km) route traverses portions of Marion and Hamilton counties in Tennessee, including the Chattanooga area.

SR 27 begins as it runs concurrently as a secret, or hidden, designation, with U.S. Route 72 (US 72) once that highway enters Tennessee from Jackson County, Alabama.

This point also marks the eastern terminus of unsigned Alabama State Route 2.

During SR 27's concurrency with US 72 in Marion County, it traverses the cities of South Pittsburg, Kimball, and the Marion County seat of Jasper, as well as the exit 152 interchange on Interstate 24, where they pick up US 64.

US 27 and SR 27 passes through downtown Chattanooga, with a brief concurrency with I-24 between exits 178 and 180, and then it turns southward, still following US 27, and for SR 27 to terminate at the Georgia state line, which in this area, it coincides with the Chattanooga city limits, as well as those of Rossville, Georgia and Walker County's northern boundary.