This species is characterized by its robust habit, rather large leaves, stipules with the lobes obtuse to rounded, pedunculate pyramidal inflorescences with red to yellow axes and reduced bracts, tubular-funnelform yellow to orange corollas, and rather small, ovoid, laterally flattened fruits. This species is widespread, found in primary vegetation but also frequent in secondary vegetation, and morphologically variable. It is part of a complex of species or forms centered in the Amazon Basin of South America, along with Palicourea grandifolia and several species found in the foothills of the adjacent Andes, including Palicourea buntingii, Palicourea semirasa, Palicourea premontana, and Palicourea flavifolia. The circumscription of Palicourea guianensis is not yet entirely clear. Steyermark separated several subspecies and varieties, and molecular data show that the species as circumscribed is polyphyletic; however the molecular data do not separate exactly the same taxa that Steyermark recognized.
Palicourea guianensis as currently circumsribed is distylous throughout most of its South American range but appears to be monomorphic (or isostylous) in the Antilles and perhaps also in Central America and in Colombia west of the Andes; molecular data suggests that these plants may comprise a separate species, but both flowering collections and molecular sampling are limited.
Palicourea guianensis as circumscribed by Steyermark is notable for its variation in number of ovary locules and styles, with 2 locules, 2 styles, and 2 pyrenes in the plants of most of its range but with some plants having 3 and some having 4 or 5 in northeastern South America; plants with different locule numbers have been separated at the varietal level by some authors, but appear to be sympatric with 2-locular plants with some variation occasionally found on individual plants.