A single incident of attempted predation of a Harbor Seal (Phoca vitulina) pup by an American Mink (Neovision vision) was observed on Blakely Island, Washington in 2015. San Juan County Marine Mammal Stranding Network members responded, investigated the event, and performed a necropsy on the seal. Predation is the most parsimonious explanation for the attack due to the American Mink's opportunistic predatory tendencies and the vulnerability of the moribund Harbor Seal. With both the American Mink and Harbor Seal populations documented as abundant or at carrying capacity, respectively, mink predation on vulnerable Harbor Seal pups could increase or influence Harbor Seal haul-out behavior.