The South Fork Tieton River begins at Meade Glacier on the eastern side of Gilbert Peak, also part of the Goat Rocks.

The South Fork collects many streams as it flows generally north, entering Rimrock Lake near its east end.

Rimrock Lake is an artificial reservoir created by Tieton Dam and managed by the U.S. Bureau of Reclamation.

The lake stores water for irrigation use as part of the Bureau of Reclamation's Yakima Project.

It flows generally east, joining the Naches River near the town of Tieton.