Sex differences in cognitive abilities are a controversial but actively researched topic. The present study examined whether sex-role identity mediates the relationship between sex and sex-typed cognitive abilities. Three hundred nine participants (105 males and 204 females) were tested on a range of visuospatial and language tasks under laboratory conditions. Participants also completed measures of sex-role identity, used to classify them into masculine, feminine, androgynous and undifferentiated groups. While sex differences were found for some but not all measures, significant sex-role differences were found for all spatial and language measures with the exception of a novel 2D Mental Rotation Task. Masculine sex-roles partially mediated the relationship between sex and a composite measure of spatial ability, while feminine sex-roles fully mediated the relationship between sex and a composite measure of language ability. These results suggest that sex-role identity may have greater utility in explaining individual differences in cognitive performance than biological sex alone.