The Dehnenkopf lies in the Upper Harz in the Harz National Park; immediately to the west is the Harz Nature Park. The Dehnenkopf rises about 1.1 km west-northwest of Torfhaus, a village in the mining borough of Altenau. To the east are the Lerchenköpfe peaks (821 m) and to the west is the Mittelberg (667.1 m). Towards the southwest the countryside transitions to the Bruchberg (ca. 927 m). On the north flank of the Dehnenkopf rise two tributaries of the River Oker: the Kalbe and the Kellerwasser, which flows through the valley of Kellwassertal. A little tributary stream of the Kellwasser, the Nabe, flows by to the west. Around 500 metres northeast of the summit runs the B 4 federal road, from which the Landesstraße 504 branches off in Torfhaus heading roughly westwards as the Steile-Wand-Straße to Altenau.