The study aims to reconstruct the development of foraminifer assemblages in the Meotian basins of the Ponto-Caspian region using new and existing data. In the Late Sarmatian period, these marine basins lost connection with the sea of normal salinity but regained it at the beginning of the Meotian, allowing Mediterranean-type foraminifers to colonize. During the Early Meotian, 32 genera and 90 species of mainly polyhaline foraminifers thrived, particularly in warm, oxygen-rich sublittoral zones. However, in deeper, colder, and oxygen-deficient areas, the foraminifers were smaller and less diverse. By the Late Meotian, the connection to normal salinity seas was lost again, leading to the decline of polyhaline foraminifers and their replacement by ostracods.