[1][3] Loop 337 begins on the southwestern side of New Braunfels at I-35, heading north through the city predominantly as a surface street with at-grade intersections.

From here and to the east, Loop 337 and SH 46 run along the northern fringes of the city limits as a concurrent, co-signed route.

As the loop turns towards the southeast, another interchange due to a railroad bridge occurs at Rock Street and Gruene Road.

After crossing the Guadalupe River, Loop 337 turns towards the south at the Common Street intersection.

The route comes to an end at I-35 on the northeastern side of the city, while SH 46 continues on to the south toward Seguin.