An abundant fauna of well-preserved holothurians is described from the Middle Triassic (Ladinian) of Collbato, northern Spain. Three new genera and species are represented, Strobilothyone rogenti, a heterothyonid, Monilipsolus mirabilis, a psolid, and Collbatothuria danieli an aspidochirote of uncertain familial affinities. A new subfamily, Monilipsolinae, is created for Monilipsolus. Holothurians had clearly achieved considerable diversity by the Middle Triassic; at least four of the six currently recognized orders were established by this time. Holothurians were also ecologically diverse by the Middle Triassic with epibenthic, deposit-feeding species, infaunal, suspension-feeding species and epifaunal, attached, suspension-feeding species all represented.