Shrubs, erect to arching, clambering, or climbing, often sparingly branched, sometimes forming impenetrable thickets. Roots diffuse, adventitious where arching stems touch soil. Stems segmented or unsegmented, green, greatly elongate, angled, 30-400[-700] × (4-)6-10 cm; ribs 3-5[-7], narrowly triangular to winglike, very prominent, 3-5 cm deep, less than 1 cm thick, rib crests undulate; areoles widely spaced, located next to sinuses, 2-5 cm apart along ribs, circular to oval, short woolly. Spines [0-]4-10 per areole, diffusely spreading, brown or reddish [white, yellowish, or black], aging gray, ± straight, acicular to subulate, terete or somewhat flattened, longest spines 10-40[-70] mm, hard; radial spines [0-]6-8 per areole, 5-25 mm; central spines [0-]1-2[-4] per areole, 0-40 mm. Flowers nocturnal, lateral to terminal on stems 1 or more years old, at adaxial edge of areoles, funnelform, [11-]14-20[-25] cm; outer tepals green or purple tinged, lanceolate-linear, 3-5 × 1 cm; inner tepals white, broadly linear to narrowly oblanceolate, 5-15 × 1-4 cm, margins entire or minutely denticulate; ovary minutely scaly, spiny [spineless], with short wool; stigma lobes 10-15, white, to 12 mm. Fruits indehiscent or irregularly dehiscent longitudinally, red to red-purple, spheric, ovoid, ellipsoid, oblong, or pyriform, 30-80[-120] mm, fleshy or juicy [tough in A. columbianus], scaly, spiny [or spineless]; scales deciduous; pulp red; floral remnant persistent. Seeds black, broadly obovoid, to 4.8 mm, smooth and shiny; testa cells flat. x = 11.

Acanthocereus needs critical taxonomic study. E. F. Anderson (2001) followed W. Barthlott and D. R. Hunt (1993) in recognizing six species; other accounts have recognized up to twelve species or as few as two (A. tetragonus and A. occidentalis Britton & Rose).