Deer Lake is a lake in King County, Washington. It is an expansion of the Taylor River, located just below its true source. Located a short distance downstream is Snoqualmie Lake. The lake is reached by hiking 1 mile from Snoqualmie Lake. Deer and Bear Lake are both about the same size. The river drops over a small waterfall just before flowing into the lake. Shortly below the outlet is a long cascade that likely extends much of the way to Snoqualmie Lake.