Animals’ body size varies intra-specifically and geographically among populations, and many species (including small carnivores) show sexual dimorphism and larger individuals (lower superficial area/volume ratio) inhabiting cooler climates complying with Bergman’s rule. In the present study we analyse data of common genets wild-caught in three different regions of the Iberian Peninsula, searching for variations in size and weight between males and females, testing for sexual dimorphism, as well as for micro-scale geographical variations among populations in biometrics and sexual dimorphism. We use field measurements such as length (body and tail) and weight, to characterise the three populations in the Iberian Peninsula. Our results show that Iberian genets present significant differences between sexes, although sexual dimorphism is lower than in other small carnivores, and that they comply with Rensch’s rule, males size showing greater variation. Iberian genets also follow the Bergman’s rule, being bigger and heavier in colder and northern regions. Although we have detected morphometric differences among studied populations, sexual dimorphism indexes varied little. We discuss our results in the light of the different hypotheses given to explain the sexual dimorphism in carnivores, trying to identify the mechanisms that might play a role in the dimorphism of genets.