Val Poschiavo can be reached from the Upper Engadin valley in the north via Bernina Pass (Passo del Bernina) and from the Italian comune of Livigno via Livigno Pass. In the south it stretches down to the village of Campocologno at the end of the valley, bordering directly on the Italian town of Tirano. Beneath Bernina Pass, the Val di Campo mountain valley leads up to Val Viola Pass in the northeast.
The valley is drained by the Poschiavino river, flowing through Lago di Poschiavo. Smaller lakes in its basin include Lago Bianco, Lago di Saoseo, and Lago di Val Viola. From north to south, the valley descends from an altitude of 2,300 m (7,500 ft) to 550 m (1,800 ft), passing through different altitudinal zones. The surrounding mountains of the Bernina Range and the Livigno Alps include the Piz Palü, 3,901 m (12,799 ft), Piz Cambrena, 3,606 m (11,831 ft), Piz Varuna, 3,453 m (11,329 ft), and Piz Lagalb, 2,959 m (9,708 ft).