This species is characterized by its medium-sized to usually robust leaves; stipules with broadly triangular to ligulate, obtuse to rounded lobes and a sheath that begins as concave then widens into subtruncate; well developed stout peduncles; well developed narrowly pyramidal to cylindrical, paniculiform red to yellow inflorescences with (18-40+) usually closely set, slender, secondary axes that are branched to several more orders; pedicellate flowers; short calyx limbs; tubular medium-sized yellow to red corollas that are externally glabrous or shortly hirtellous; and ellipsoid rather small flattened fruits with 2 pyrenes. The stipules and the stems near them generally have a covering of a dried mucilaginous substance. The leaves are characteristically shiny abaxially and sometimes on both sides. The inflorescence are erect and showy. Several specimens are notable (in Palicourea) for their inflorescences bearing apparently mature fruit, flowers at anthesis, and flowers in bud all together; this suggests that the inflorescences of this species may be long-lived.
Palicourea sellowiana has been included in the circumscription of Palicourea guianensis by Standley in herbarium determinations and subsequent workers. More material now shows that Palicourea guianensis differs in its corollas that are externally pustulose to densely puberulous with stout colored trichomes, inflorescences with fewer secondary axes, and range in the Amazon basin and northward. These species may be be sympatric in the brejos of Pernambuco, but the material from there has not been studied in detail yet.
The Sellow specimen in the general collection at G was formerly deposited in Candolle's herbarium and annotated by him as Palicourea sellowiana, and has two separated leaves and part of an inflorescence. This specimen was annotated by Taylor as probably the isotype of this species based on the assumption that the holotype specimen was filed in the G-DC collection because it was described in his Prodromus. However, there is no specimen documented there of Palicourea sellowiana in the microfiche index, so this other specimen in G may be the holotype. A duplicate, complete specimen of this was deposited at B (and subsequently destroyed, F neg. #635), but not annotated by anyone with this name so it may not have been seen by Candolle.
Palicourea sellowiana is also similar to Palicourea longepedunculata, which is also found in eastern Brazil but differs in its pendulous usually smaller inflorescences with longer flexuous peduncles and the secondary axes only shortly branched into 3--9-flowered cymes, and stipules with the triangular lobes acute and the sheath acute to truncate. Palicourea sellowiana is also similar to Palicourea grandifolia of the Amazon basin, but that species differs in its usually shorter inflorescences with fewer secondary axes, corollas externallly densely puberulous with stout colored trichomes, 4-5-locular ovaries, and fruits with 4-5 pyrenes.