The first two miles of the route runs concurrently with SR 41.

The total length of SR 133 is 28.76 miles (46.28 km).

Routes 133 and 41 run concurrently for about two miles (3.2 km) in Winthrop.

After splitting from SR 41 in Winthrop, the road heads west towards Wayne, where it meets the eastern end of SR 219.

After the SR 219 junction, it heads north to the northern end of SR 106 at Livermore Falls.