The route passes over the Allegheny Valley Railroad's W&P Subdivision line and comes to an intersection with PA 519 in Eighty Four, at which point it crosses into Somerset Township.

[1][3] Here, the route turns east into Carroll Township, passing through woodland and coming to an interchange with the PA 43 toll road, where it becomes a divided highway.

Following this interchange, PA 136 becomes undivided and heads through wooded areas with some homes, crossing under a Wheeling and Lake Erie Railway line and passing through Baidland.

The road runs east-northeast through areas of fields and woods with some homes, curving east into woodland as it forms the border between the borough of New Eagle to the north and Carroll Township to the south.

The three routes intersect PA 481 and become East Main Street, crossing Norfolk Southern's Ellsworth Secondary railroad line.

After leaving the Monongahela City Bridge, the route briefly becomes a divided highway and curves east-southeast onto Bunola River Road.

Farther east, the route passes between woods to the north and the railroad tracks to the south, coming to an intersection with PA 906 in Milesville.

[1][5] PA 136 enters Rostraver Township in Westmoreland County and becomes an unnamed road, running through more farmland and woodland with a few homes and curving east-southeast.

Here the route becomes East Main Street and crosses CSX's Keystone Subdivision railroad line, heading through the commercial downtown of West Newton.

The road runs through areas of homes with some commercial development, passing over I-76 (Pennsylvania Turnpike) before turning northeast and entering the borough of Arona.

The route becomes West Newton Road and is two lanes again as it passes more homes, crossing the Southwest Pennsylvania Railroad's Radebaugh Subdivision line.

PA 136 continues east through dense residential areas and becomes the border between the city of Greensburg to the north and Hempfield Township to the south.

The route becomes a divided highway and ends at an interchange with the US 30 freeway, with West Newton Street continuing east toward downtown Greensburg.