The township borders the Morris County municipalities of Mountain Lakes and Parsippany-Troy Hills to the east, Morris Township to the South, Randolph to the south and west, Rockaway Borough to the west, Rockaway Township to the north and west, and Boonton Township to the north and east.
Denville has 11 named bodies of water within township limits. The four major residential lake communities are Cedar Lake, Indian Lake, Rock Ridge and Lake Arrowhead (including Great Bay and Bay of Deep Waters). Estling Lake is a private summer community. The three minor lakes are Cooper Lake, Hollstein Lake, and Openaki Lake. The town also has Cooks Pond, a recreational lake available for public use by membership.