This species is characterized by its glabrous rather slender habit, costate stems, lanceolate rather small leaves without domatia on rather short petioles, few- to several-flowered short cymose inflorescences, small white to cream flowers, and small white fruits with angled to weakly ribbed pyrenes. The inflorescence are mainly terminal but sometimes also apparently produced at lower nodes in a pseudoaxillary position, and not displaced to that position by later growth. The leaf margins are frequently crisped at least on dried specimens. It is commonly collected in several sites and apparently sometimes locally common, including at Ambotavy.

This species was included by Bremekamp in his Psychotria Group II, which was characterized by its relatively narrow leaves. The leaves of Psychotria andevorantensis are lanceolate and less narrow proportionally than the other species of Group II, however these leaves are also rather small and thus in absolute terms they are narrow. Psychotria andevorantensis is similar to Psychotria taxifolia of this group and has been confused with it, however Psychotria taxifolia has linear or linear-lanceolate leaves with the lateral margins mostly straight, while Psychotria andevorantensis has leaves with the margins curved. Bremekamp also separated these based on petiole length, but more recent collections show more variation in this and in the leaf length of Psychotria taxifolia than he saw and this character does not completely separate these. Psychotria andevorantensis is also similar to the species of Bremekamp's Psychotria Group VI, in particular Psychotria ivakoaneyensis.