[1] The North Branch Belle River rises out of Long Lake at 43°00′50″N 83°08′41″W / 43.01389°N 83.14472°W / 43.01389; -83.14472 (North Branch Belle River (source))[4] in section 22 of Attica Township in southeast Lapeer County.

From Long Lake, the river flows eastward around the north side of Imlay City.

It is fed by the Hunt, Pennell, and Clark Corner drains on the northeast of Imlay City and turns southward, where it joins the main branch of the river at 42°59′31″N 83°03′57″W / 42.99194°N 83.06583°W / 42.99194; -83.06583 (North Branch Belle River (mouth)), now near the intersection of Interstate 69 and M-53.

The river continues east by southeast through China Township and into East China Township, where it turns south less than a half mile from the St. Clair River and parallels the St. Clair for a few miles before its mouth in downtown Marine City.

The river's watershed drains portions of Lapeer, Macomb, Oakland, and St. Clair counties.