This species was described based on one incomplete specimen at US, and now three more complete collections have been seen from Ecuador. Simira mollis is characterized by its medium-sized to robust ovate leaves with a truncate to cordulate base, 12-16 pairs of secondary veins, and a densely pilosulous or villosulous undersurface; well developed caducous stipules that leave a well developed scar; a several-flowered, subcapitate, shortly pedunculate, subglobose inflorescence with ligulate to oblanceolate bracts about as the calyx limb; flowers that are pilosulous on the well developed hypanthium and calyx limb; cream-colored corollas with short rounded lobes; and woody capsules ca. 4 cm in diameter. The flowers appear to be -5-merous, but this is difficult to confirm on the material available. The calyx limb is 3-5 mm long and irregularly lobed. No mature corollas have been seen, and the flowers of a tree appear to all open at about the same time. The type specimen shows no reddish purple oxidation, although the stem cross-section is not visible in the online image; the specimens from Ecuador have all dried with a reddish purple color throughout. The type collection locality is unknown, althugh much of Mutis's material was collected in the upper Magdalena valley and the southern Cordillera Oriental. Three additional specimens from Ecuador are included here.

Simira mollis is similar to Simira erythroxlon var. saxicola, with leaves that with fewer secondary veins and calyx limbs with a leathery basal portion; this other variety (which is probably better regarded as a species) is found in humid to seasonal forest on granitic outcrops in eastern Venezuela. Simira mollis is similar vegetatively to Simira ignicola, but that species has cymose inflorescences branched to 2-3 orders and calyx limbs ca. 1 mm long that are deeply regularly lobed. Simira mollis is also similar to Simira wurdackii, with cymose inflorescences, shorter lobed calyx limbs, and leaves that are abaxially glabrous or puberulous on the principal veins.