New Oligocene and Miocene decapods from Argentina include four new Miocene species, Nectocarcinus verruculus, Cancer zameniscus, Chaceon marcorilobus, and Eurynome bandurriasensis, and one new Oligocene genus and species, Disspinamithrax santacruzensis. The new specimens also include an axiid (Ctenochelidae), and several previously named brachyurans. The Miocene fauna of the Estancia 25 de Mayo Formation shares some taxa with other Miocene faunas from Argentina but is distinct.