[1] Beginning at Long Lake in Grand Traverse County, the Platte River flows west across Benzie County before ending at Platte Bay, a small bay of Lake Michigan, in the Sleeping Bear Dunes National Lakeshore.

From Lake Ann, the Platte River runs west and south.

The main branch receives Collison Creek just east of Honor, Michigan.

At the Platte River Campground in the state forest, the river turns north west flowing toward Platte Lake.

The river above Platte Lake tends to be much swifter and colder than the lower stretch, which is warmed considerably by its passage through the relatively shallow, 3-mile (4.8 km) stretch of Platte Lake.