European and American minks (Mustela lutreola and Neovison vison, respectively) are very similar in their ecology, behavior and morphology. However, the American mink is a generalist predator and seems to adapt better to anthropogenic effects, allowing it to outcompete the European mink in areas where it has been introduced, threatening the survival of the native species. To assess whether differences in the masticatory apparatus allow American mink to exploit a wider range of food items than European mink, we analyzed shape variation in the cranium of both species using 3D GMM. A set of 37 landmarks and 107 semilandmarks was digitized on each specimen and, after superimposition, shape variation was explored with Principal Component Analysis. Differences in size and shape between and within species were assessed with Procrustes ANOVA. European minks were shown to have a relatively smaller face with a shorter and wider palate, a slightly longer and narrower neurocranium, and broader and less curved zygomatic arches. Covariation between size and shape was also noted, with small specimens with globous neurocrania and large specimens with marked airorhynchy and well-developed sagittal and nuchal crests. In bigger specimens the face and palate expand (to accomodate bigger teeth), as do the origins of the masticatory muscles. Significant differences between species were found in cranial shape, but not in size. Within species, males and females were significantly different both in size and shape. Overall, differences in cranial shape between species suggest that American mink have stronger masticatory muscles (i.e., higher bite forces) and a wider gape than European mink, which would increase the range of their diet (bigger prey, tougher shells) and also make them more efficient at killing small prey.