This species is characterized by its medium-sized leaves (for Manettia) that are paler and smooth abaxially, with the venation not evident, its calyx lobes of average length (0.5-2.5 mm), and its distinctive corollas that are short with a rather stout tube 2-3.5 mm long and have the lobes as long as or longer than the tube and densely hirsute on the adaxial (inner surfaces), and is found in premontane and montane vegetation. Most other Manettia species that are found at higher elevations have corolla lobes that are glabrous or puberulent on their adaxial surfaces, at least in Central America.

Manettia barbata is similar to Manettia flexilis, which is found at similar elevations and also has the corolla lobes pilose or hirsute adaxially; Manettia flexilis differs in its longer corollas with the slender tube 4-5 mm long and the lobes about as long as or shorter than the tube. Manettia barbata is also similar to Manettia alba, which is found at lower to middle elevations in eastern Veneuzela, the Guianas, and northeastern Brazil and has similar corollas; Manettia alba however differs in its leaves that are not markedly paler abaxially and have the venation closely reticulated and prominulous to prominent.

Steyermark (1972: p. 241) recognized two varieties of Manettia barbata, but did not provide a key to these nor a treatment of the whole species. He studied plants from Costa Rica and from Venezuela, and concluded that the Costa Rican plants are characterized by stipules that are "more elongated in the middle with a bicuspidate apex and more erose margins, the calyx lobes relatively narrower or longer proportionately (1-1.5 x 1 mm)" and "the inflorescences less branched and with fewer flowers (1-7), vs. in the Venezuelan plants stipule lobes 1.5-2 x 1.1-1.5 mm and "more compoundly branched inflorescences with more numerous flowers (12-14) or more). He noted that the flowers are the same size in both populations. Steyermark reported this species only from these two areas, but it is expected also in Colombia and if present, those populations need to be included in this analysis. There is variation in inflorescence form in the Venezuelan plants that encompasses the form of the Costa Rican inflorescences (e.g., Meier et al. 8659, MO). The stipule characters seem minor. However there is geographic separation of these populations, so Steyermark's varieties are provisionally recognized here pending further study of this species.