National Secondary Route 138, is a road between Route 4 and Route 35, contained in the north plains of the Alajuela province of Costa Rica.

It is the main access route to the Caño Negro Wildlife Refuge.

The entire route is in Alajuela province.

In May 2020 the segment between Caño Negro Wildlife Refuge and Route 35, was asphalted for a total of 18.2 km (11.3 mi).

This article about a road in Costa Rica is a stub.