The first fossil occurrence of the genus Lepidobatrachus is reported. The specimen comes from the Farola Monte Hermoso locality (Buenos Aires Province, Argentina), more specifically from the early Pliocene levels of the Monte Hermoso Formation. The specimen belongs to the living species L. laevis, a frog that currently inhabits the Chacoan region of northern Argentina, Paraguay, and Bolivia. The presence of this anuran represents the southernmost record for the genus Lepidobatrachus, and is in agreement with previous hypothesis suggesting that during the Pliocene the climatic environmental conditions of the southern Pampas were likely those of the modern Chacoan region. The disjunct distribution of extant L. laevis suggests that the retraction of Chacoan areas to the north modified the former distribution of this taxon, and that its current geonemy may represent relics of a formerly more extensive geographic distribution.