The Mashel River's headwaters are a tiny, unnamed lake about northwest of Mount Beljica. The river starts off as a small stream flowing northwest before turning west then south, where the South Fork Mashel River joins, after which the Mashel turns west. The Mashel River is joined by Busy Wild Creek and then, about 3.5 miles downstream, Beaver Creek. The Mashel continues west for about 2.7 miles then turns southwest, along the southern city limits of Eatonville, which it follows for about 1.7 miles. The river is joined by the
Little Mashel River a mere after leaving Eatonville's city limits. George Smallwood Park, named for one of the former mayors of Eatonville, is located about 0.8 miles above the Little Mashel River confluence. After the Little Mashel confluence the Mashel flows west for another 1.1 miles before passing under Highway 7 and gradually turning south and emptying into the Nisqually River. == South Fork ==