Egernia stokesii is a monogamous and group-living species of Australian scincid lizard. We used genotype data from 10 microsatellite loci to examine evidence for sex-biased dispersal and kin-based discrimination as mechanisms for inbreeding avoidance of E. stokesii within seven rocky outcrops in the southern Flinders Ranges of South Australia. We also examined the relatedness of individuals observed using the same crevice within groups. We found no evidence for sex-biased dispersal at these sites, but found that adult lizards of the opposite sex observed using the same crevice were less related to each other than expected by chance. Our results suggest a behavioural mechanism for minimising inbreeding in large related aggregations of this species.