Diodella includes weedy herbs with distinctive interpetiolar stipules, which are fused to the petioles or leaf bases on each side with the sheath truncate to rounded and setose (i.e., with 3-11 or so bristles or linear appendages or setae); generally rather scabrous leaves; axillary inflorescences with 1 or a few sessile, rather small, homostylous flowers; 4 calyx lobes, corolla lobes, and stamens; and schizocarpous fruits, with two rounded mericarps that split and fall off the plant, and each remain indehiscent. The stipules are similar to those of several other genera, including Mitracarpus, Spermacoce, and Oldenlandia.
The species of Diodella have generally been included in the basically Neotropical genus Diodia, which was circumscribed broadly until recent years. The systematics of this and related genera are not well understood, but molecular studies generally indicate that Diodia as broadly circumscribed was polyphyletic, and several groups have been recently separated based mainly on morphological characters (e.g., Bacigalupo & Cabral 1996, 2006).