The Cassidulinidae is a family of Paleocene to recent benthic foraminifera (amoeboid protists) that make up part of the rotaliid superfamily Cassidulinacea, characterized by calcareous test with biserially arranged chambers in a planispiral coil, at least in the early stage, but which later may uncoil.
The Cassidulinidae includes three subfamilies, the Cassidulininae, Ehrenbergininae, and Orthoplectinae, which contain as many as fourteen (14) genera.