This species is characterized by medium-sized stiff-textured leaves, subsessile to shortly pedicellate 5-merous flowers, a dentate calyx limb 0.8-1.2mm long, and green to whitened or yellowish green corollas with the slender tube 14-19 mm long. The corolla tubes are quite cylindrical, and the lobes are relatively short and and form an abrupt cushion-shaped structure on the top of the bud. Fedinandusa uaupensis is similar to Ferdinandusa chlorantha, and these have been extensively confused.

Ferdinandusa chlorantha is much more common, and has 4-merous corollas with the lobes relatively longer and the tube a bit stouter and more funnelform in bud, and generally shorter calyx lobes. Ferdinandusa uaupensis also often has leaves with the secondary veins more pronounced and the surface even sometimes weakly bullate, but the separation of species of Ferdinandusa based on vegetative characters is problematic for all the species except Ferdinandusa elliptica. Anunciação reported Ferdinandusa uaupuensis only from the Rio Negro basin, but she annotated various MO specimens from the Ecuador and Peru with this name, but did not cite them in her treatment; hese all have four-merous flowers, and are here included in Ferdinandusa chlorantha.