Known as Max Meadows Road, the state highway runs 1.83 miles (2.95 km) from Interstate 77, I-81, U.S. Route 11, and US 52 at Fort Chiswell north to SR 1004 and SR 1006 in Max Meadows in eastern Wythe County.

US 52 runs concurrently with the three other highways west to Wytheville and heads south from the interchange as Fort Chiswell Road toward Hillsville.

SR 121 starts as a four-lane divided highway within the interchange but immediately reduces to a two-lane undivided road to head north to Max Meadows.

The state highway crosses Reed Creek before entering the village, where it reaches its northern terminus at its intersection with SR 1004 (Ayers Street) and SR 1006 (Max Meadows Road) immediately to the north of its grade crossing of Norfolk Southern Railway's Pulaski District rail line and one block south of SR 610 (Peppers Ferry Road).

[1][2] SR 121 was numbered in the 1933 renumbering as an extension of U.S. Route 121 (now US 52 south of Fort Chiswell).