Seventeen species of decapod crustaceans have been described from Campanian through Paleocene rocks in the Santa Marta, López de Bertodano, and Sobral Formations of the James Ross Basin, Antarctica. Of these, nine are new species: Metanephrops rossensis, Glyphea australensis, Paguristes santamartaensis, Munidopsis foersteri, Retrorsichela laevis, Plagiophthalmous collinsi, Rhinopoupinia bicornis, Cristafrons praescientis, and Torynomma (Torynomma) australis. One new family, Retrorsichelidae, and three new genera, Retrorsichela, Rhinopoupinia, and Cristafrons, were also named. This assemblage includes the first notice of brachyurans from the Cretaceous of Antarctica; six species are described. The nephropid lobster Hoploparia stokesi (Weller), the most common decapod throughout the section, exhibits significant morphological change throughout its range from late Santonian or earliest Campanian to Paleocene; however, variation of key features is asynchronous. The raninid brachyuran, Cristafrons praescientis, is second in abundance to H. stokesi. The occurrence of Metanephrops rossensis and Munidopsis foersteri represents the oldest geological records for these genera and the recognition of species of Paguristes, Plagiophthalmous, Torynomma, and Necrocarcinus constitutes the first notice of these genera in Antarctica. Of those taxa that have living congenors, the species of Metanephrops, Linuparus, and Munidopsis occupied habitats at inner shelf depths in the Cretaceous whereas their extant descendants are restricted to outer shelf and bathyal depths. This diverse decapod fauna is dominated by genera that range into the Cenozoic and appears to be a pioneer assemblage.