Faramea neilliana is characterized by the combination of its medium-sized, elliptic leaves with continuous, rather well-developed submarginal veins; deciduous, well-developed stipules with short aristas; terminal, paniculiform inflorescences with reduced bracts and several dozen pedicellate flowers; short, dentate calyx limbs; salverform, medium-sized, blue or lilac corollas; and medium-sized, oblate, laterally flattened fruits that often have unusually stiff walls when they are immature. The specimens usually dry with a gray cast. The stipules are fused for most of their length into a tube that splits along one side, forming a distinctive spathaceous structure that becomes dried and fragmented. The stipules are fused for most of their length into a tube that splits along one side, forming a distinctive spathaceous structure that becomes dried and fragmented. The basalmost pair of secondary axes are subtended by bracts that are variously reduced, stipuliform, or foliaceous. The corollas are thin-textured and pale in color but consistently described as blue to violet. The immature fruits are often distinctive in their apparently stiff walls, which shatter when pressed, but the mature fruits are fleshy as in other species of the genus.
Faramea neilliana is similar to Faramea multiflora, which differs in its shorter stpules, more fleshy corollas, and smaller fruits that lack stiff walls. Faramea neilliana is also similar to Faramea oblongifolia, which can be separated by its similar but usually shorter stipules, with the sheath portion 4–15 mm long; inflorescences with usually fewer flowers, about one to three dozen; larger, white corollas with cylindrical tubes 12–18 mm long and ovate lobes; and immature fruits with papery walls.