It drains a watershed of 912 square miles (2,360 km2), consisting of mountains and forests, and valleys filled with large lakes and wetlands.

The river exits from the southwestern corner of the lake at McCall and flows southwards through Long Valley into Lake Cascade, a large reservoir formed by Cascade Dam.

[5] About five miles (8 km) below the Cascade Dam and the town of Cascade, the North Fork reaches the end of Long Valley and enters a narrow canyon along the western side of the North Fork Range in the Boise National Forest.

Paralleled by State Highway 55, it crosses into Boise County, where the canyon's depth exceeds 2,500 feet (760 m).

[5] Media related to North Fork Payette River at Wikimedia Commons