We present the first finding in Uruguay of the recently described frog Physalaemus cristinae. Adult specimens were collected in two localities of north-western Uruguay, on the east bank of the Uruguay River: near the city of Bella Unión associated to temporal ponds of an agricultural area; and in an urban area within the city of Salto. The advertisement call consisted of a single and non-pulsed note, characteristic of P. cristinae. In addition, partial sequences of the cytochrome b gene confirmed the species identity. We consider that the presence of P. cristinae in north-western Uruguay, previously unregistered in a well sampled area, is due to recent cross-river dispersal from populations in the Provinces of Entre Ríos and Corrientes, Argentina, on the west bank of the Uruguay River.