This species is characterized by its somewhat robust habit and often dark brown drying color; its obovate to oblanceolate, rather stiff-textured leaves that are obtuse to acute at the base and obtuse to usually rounded or truncate at the apex with the venation visible; its interpetiolar stipules with two narrow to aristate lobes; its pedunculate, corymbiform, several-flowered inflorescences with the flowers sessile or subsessile but often separated on dichasial axes; its rather short yellow corollas; and its medium-sized red fruits. This name has not been used much since Bremekamp's revision of these species, but as circumscribed here this is one of the most commonly collected species of Psychotria in Madagascar. There is variation in the plants included here in leaf size, number of secondary leaf veins, and number of flowers in the inflorescences, and also some variation in stipule and calyx limb size. However no morphologically distinct groups can be separated at least at present. Bremekamp described this species based on a rather small number of specimens; most of the numerous collections now available were made during quite recent explorations.

Psychotria imerinensis is similar in general aspect to Psychotria andriantiana, and these have been confused in herbarium identifications; however Psychotria andriantiana is only known from northern Madagascar where it is sympatric with Psychotria imerinensis but quite uncommon, and Psychotria andriantiana can be separated by its leaves that are generally rounded to truncate at the base, its white corollas that are twice as large as those of Psychotria imerinensis, and its fruits that become white then blue or blue-black. Psychotria imerinensis is also similar to Psychotria reducta and Psychotria retiphlebia, and the separation of these here is perhaps arbitrary: these are separated here based mainly on leaf shape, relatively broader and usually larger with the apex broadly obtuse to truncate in Psychotria imerinensis, vs. relatively narrow and generally smaller with the apex mostly acute in those other species. Psychotria imerinensis has also been confused with Psychotria parkeri, but Psychotria parker has leaves that are generally at least shortly acuminate at the apex and the stipules united around the stem into a tube with one triangular, entire to denticulate lobe on each interpetiolar side.