Aloe nubigena is small, soft-leaved and medium to fast-growing. The plants proliferate from the base forming small clusters, usually hanging from cliffs. The stems are horizontal to drooping (pendulous), up to 100 mm long and covered with old dry leaf remains. The green functional leaves are produced in an apical rosette, often borne in two opposite rows (distichous). They are linear and pendulous and are up to 600 mm long and 20 mm in diameter. The leaf margins are entire or sometimes beset with very small soft teeth (denticulate) in some populations. The leaf surface is green and smooth. The inflorescence consists of a simple spreading to spreading-pendulous raceme up to 210 mm long. The flowers are tubular (27 × 7 mm), drooping, orange-red in colour with green tips and are borne on pedicels about 30 mm long. The fruit is an oblong-conical capsule 20 × 10 mm. The seeds are angular, 3 × 1,5 mm and dark brown. Aloe nubigena is one of the 24 grass aloe species confined to South Africa.