Sex is a pervasive factor that underpins functional phenotypic variation across a range of traits. Although sex can usually be distinguished morphologically, in some species this is not possible. The development of genetic markers for sex identification is, thus, key if we are to incorporate sex into an understanding of ecological or evolutionary process. Here we develop genetic markers for the identification of sex within an iconic Australian lizard group, the Egernia group, which is notable for its complex social behaviour. We used restriction-site associated DNA sequencing to characterise sex-specific genetic sequences for a key member of the group, Liopholis whitii, and designed primers for four of these putative sex-specific sequences. These primers amplified across some, but not all, species of the group. Our results provided several important insights. They suggest conservatism of a XX/XY sex determination system within the group as well as sex-specific genomic regions that appear independent of the conserved genomic regions identified in other skink species. More broadly, the development of sex markers for the Egernia group opens up a range of potential research questions related to the role that sex plays in the mediation of social behaviour and, through this, the emergence and stability of social life.