Phimophis guerini Duméril, Bibron & Duméril, 1854 is a Xenodontinae snake distributed in Argentina, Brazil and Paraguay. In Brazil, the species is broadly distributed, occurring mainly in open areas of the Cerrado, but also in the Amazon, Atlantic forest and Caatinga. We provide a new record for this species from the municipality of Santarém in the western portion of the state of Pará (Brazil). Five specimens were collected in a small area covered with Amazonian Savanna vegetation. We also provide the description of the morphological variation for the collected specimens. The new record extends the northern limit of the distribution by some 640 km (from Floresta Nacional de Carajás, Parauapebas municipality, eastern Pará). The record from Santarém provides a third locality for P. guerini within the Amazon biome and supports the hypothesis of a past ecological corridor linking the Cerrado and the open habitats within the Amazon.