Its western terminus is at the Michigan state line, where an unnumbered county highway (Morenci Road, formerly M-120) continues west-northwest.

The route then turned south on Main Street and Holland-Sylvania Road to leave Sylvania.

At Cherry Street, the route turned south, traveling through Downtown Toledo and over the Maumee River.

SR-120 then used Main Street, Starr Avenue and East Broadway to make its way to current State Route 51 (Woodville Road).

Route 120 then traveled along Woodville Road from Toledo to its eastern terminus 5 miles (8.0 km) east of Elmore.

[3] The section from Sylvania to near Ottawa Hills (Main Street/Holland-Sylvania Road) was designated as State Route 333 (now defunct).