This species is characterized in general by its medium-sized to somewhat small leaves; its terminal, often rather lax inflorescences with several somewhat small flowers borne on well developed axes and pedicels; and its somewhat small fruits. Mouly & De Block (2008) separated this species by its triangular stipules; its triangular bracteoles that are borne singly along the pedicels; its calyx limb with the tube developed and subtruncate or shallowly lobed; and its fruits that are black at maturity. Several plants of Madagascar seem to match these criteria; the distributional information here is based on the plants collected in dry and littoral forest at generally low elevations, with a few specimens in young fruit from humid forest at ca. 900-1000 m excluded. The leaf shape varies somewhat markedly within this species, from generally ovate or broadly elliptic-oblong to occasionally very narrowly elliptic-oblong.
This species is very similar to and sometimes sympatric with Tarenna grevei. De Block (2005: p. 113) discussed their separation in detail. Among other differences, Tarenna grevei has two usually seeds with entire endosperm and a large circular indentation in each fruit and corollas about 10-15 mm long with four lobes, while Coptosperma nigrescens has one subglobose seed with deeply ruminate endosperm and a rugose or smooth seed coat in each fruit and corollas about 8-10 mm long with five lobes.