The objective of this study was to determine the feeding strategies used by fossil pinnipedimorphs, test evolutionary hypotheses to understand the evolution of each strategy, and conduct comparative phylogenetic analyses on the evolution of diet and feeding strategies in Phocidae. Three-dimensional landmark data were collected from fossil pinnipedimorphs and extant phocids. Principal Component Analysis was performed to describe the major axes of cranial and mandibular variation in the dataset. The OUCH method was used test six evolutionary hypotheses. The ancestral state prey type and feeding strategy were reconstructed using maximum parsimony and Bayesian methods. This was the first study to provide quantitative and qualitative evidence for feeding strategies in extant and extinct pinnipedimorphs. Knowledge of feeding strategies in phocids is fundamental to understanding the adaptations that allowed pinnipeds to reinvade the marine ecosystem.