This species is characterized by its generally glabrescent vegetative structures, medium-sized obovate leaves, stipules not known, subsessile to shortly pedicellate flowers, calyx lobes 0.5-0.8 mm long, corollas 2-2.5 mm long, and capsules 5-7 x 1-1.5 mm.  Alseis smithii is similar to Alseis microcarpa, Alseis pickelii, and Alseis reticulata.

Humid, at least sometimes seasonal forest at 100-400 m in Guyana, generally on rocky or brown sand substrates.