Biogenic structures, herein interpreted as coprolites, were recorded in the ?upper Paleocene–Eocene Las Flores Formation, southeast Argentina. The coprolite origin is supported by several features, such as recurrent extrusive external morphology, longitudinal wrinkles, flattening of the ventral side, concentric and radial cracks, cryptocrystalline groundmass, and a phosphatic composition. A detailed comparative study with modern fecal masses, based on morphology, surface texture, micromorphology, mineralogical and chemical composition, suggest a crocodylian as the most probable producer, an interpretation also supported by the Patagonian paleontological record. This discovery, the first record on coprolites from Central Patagonia, provides new paleoenvironmental and paleoecological information for the studied successions.