Understanding patterns of body size variation is a fundamental goal in ecology, but although well studied in the terrestrial biota, little is known about broad-scale latitudinal trends of body size in marine fauna and much less about the factors that drive them. We conducted a comprehensive survey of interspecific body size patterns in coastal cephalopod mollusks, covering both hemispheres in the western and eastern Atlantic. We investigated the relationship between body size and thermal energy, resource and habitat availability and depth ranges. Both latitude and depth range had a significant effect on maximum body size in each of the major cephalopod groups (cuttlefishes, squids and octopuses). We observed significant negative associations between sea surface temperature (SST) and body size. No consistent relationships between body size and either net primary productivity (NPP), habitat extent (shelf area) or environmental variation (range of SST and NPP) were found. Thus, temperature seemed to play the most important role in structuring the distribution of cephalopod body size along the continental shelves of the Atlantic Ocean, and resource availability, seasonality or competition only played a limited role in determining latitudinal body size patterns.