A new species of Pseudoloris (Primates, Microchoerinae, Omomyidae) is described from the middle Eocene (Robiacian) locality of Mazaterón (Almazán Basin, Spain). Pseudoloris cuestai is characterized by its medium size, high and thick paracristid and absence of a distinct paraconid in the lower molars, large hypoconulid in the m3, well-developed protocone in the P3 and P4, reduced hypocone and presence of a weak postprotocingulum in the M1-2, and especially by the lower incisor, with a buccolingually enlarged crown and a very wide, anteroposteriorly compressed root. The material from Mazaterón constitutes the only record of the subfamily Microchoerinae in the Western Iberian Bioprovince, and is clearly different from the species of Pseudoloris that appear in the middle and late Eocene in the Pyrenean basins (P. isabenae from Capella, P. parvulus from Sosss, and the recently described P. pyrenaicus from Sant Jaume de Frontany). This discovery reinforces the endemic nature of the mammal faunas from this bioprovince, already observed in other groups such as Perissodactyla, Artiodactyla, Rodentia, and also evidenced in adapoid primates, with the recent description of the genus Mazateronodon. © 2012 by the Society of Vertebrate Paleontology.