This species is characterized by its shrub habit, somewhat small ovate leaves with bullulate blades and short petioles, relatively somewhat short inflorescences, subsessile to shortly pedicellate flowers borne singly and in congested groups of 2-3, deeply lobed calyx limbs with narrowly triangular lobes 1-2 mm long, white corollas with funnelform tubes 5-6 mm long and ovate lobes 2-3 mm long, and 4-locular white fruits. The leaves are hirtellous to pilosulous on the lower surface, with the lamina surface visible. The bullulate leaf blades often appear rather smooth on the upper surface but on the lower surface have prominent, regularly arranged tertiary venation.

Gonzalagunia sororia is sometimes confused with Gonzalagunia dependens, which is found in similar habitats in much of its range; Gonzalagunia dependens however has leaves that are densely lanose on the lower surface. Gonzalagunia sororia is also similar to Gonzalagunia discolor, which has leaves with only the secondary axes impressed and no tertiary venation visible.