Among mammals, primates and carnivorans possess larger brains for their body sizes relative to other clades. Several factors, such as environmental complexity (Cognitive Buffer Hypothesis), degrees of sociality (Social Brain Hypothesis), and diet quality and metabolism (Expensive Brain Hypothesis) have been proposed as mechanisms for encephalization. While studied extensively in Primates, in Carnivora predominantly the Social Brain Hypothesis has been tested. We examine whether predictions made by the Cognitive Buffer and Expensive Brain Hypotheses account for variation in brain size among extant carnivorans. Under the Cognitive Buffer Hypothesis, we predict a positive correlation between brain size and environmental variation. Under the Expensive Brain Hypothesis, we predict brain size and meat consumption will be positively correlated. Relative endocranial volume (PGLS residual from species mean body mass) and 9 environmental and/or dietary variables were collected from the literature for 148 species of terrestrial carnivorans. Environmental data was sourced from GIS maps provided by WorldClim, North American Data Atlas, and NASA/GSFC. We found no significant relationship using PGLS regression between any of the environmental and dietary variables with relative brain volume. These results suggest that carnivoran brain volumes do not support the Cognitive Buffer nor Expensive Brain Hypotheses; however, we cannot rule out simultaneous effects of both hypotheses. The strong phylogenetic signal within brain volume and body size suggests that these traits are under some form of selection, which may differ among clades. Future analyses of individual carnivoran clades may, therefore, be more conclusive.