Th e diverse representatives of Recent seals within the three extant subfamilies (Cystophorinae, Phocinae, Monachinae) of the family Phocidae exhibit dietary variations among species, feeding on invertebrates and a diversity of prey depending on the season and availability. To explain this variability, an introductory morphological examination of the mandibular structure of Recent seals from each subfamily was performed, focusing on: heights of the mandibular ramus and condyloid process; measurements of the masseteric fossa; and attachments of muscles of mastication. Aft er measuring the condyloid angles (the inclination of the condyloid process in relation to the axis of the alveolar row) among the examined species, a correlation between the size of the angle, function, and diet was recognized. Seals with a tall mandibular ramus and greater condyloid angle (Cystophorinae) feed on larger-sized prey, while seals with a shorter ramus and lesser condyloid angle feed on small (Monachinae) to medium-sized (Phocinae) prey, regardless of the overall size of the seal. Th is study focused on the mandibular morphology of some living and fossil representatives of Phocidae, providing an association between functional and ecological interpretations of modern seals in general and extrapolating this knowledge for fossil dietary preference.