A primary contention of evolutionary models of the Dark Triad traits (i.e., narcissism, psychopathy, and Machiavellianism) is that they are adaptations for dealing with adverse socioecological circumstances. In this study (N = 557), we collected data from two countries that differ in socioecological conditions (i.e., Turkey and Australia). We measured perceptions of a dangerous and competitive world and individual differences in the Dark Triad traits. Turkish participants were higher in the Dark Triad traits than Australian participants were. All the Dark Triad traits were correlated with a competitive but not a dangerous worldview. Country-level differences in the Dark Triad traits were mediated by competitive worldviews, but not dangerous worldviews, and those effects were similar in each sex. And rates of narcissism depended on participant's sex and country. This study provided the first attempt to understand country-level differences in the Dark Triad traits using a life history framework. •Turkish participants were higher on the dark traits than Australians.•Turkish participants had more competitive/dangerous worldviews.•Country-level differences were mediated by competitive worldviews.•These mediation effects were stronger in men than in women.•Sex differences in narcissism were only found in Australia.