Previous work has demonstrated that both leaders and other individuals vary in dispositional levels of physical aggression, which are genetically influenced. Yet the importance of individual differences in aggression for attitudes toward foreign policy or context‐laden moral choices, such as sacrificing the lives of some for the greater good of many, has yet to be fully explored. Given the global importance of such decisions, we undertook this exploration in a sample of 586 Australians, including 250 complete twin pairs. We found that individuals who scored higher on Buss–Perry's physical aggression scale were more likely to support aggressive foreign policy interventions and displayed a more utilitarian moral calculus than those who scored lower on this scale. Furthermore, we found that the majority of variance in physical aggression lay in genetic factors for men, whereas the majority of the variance was in environmental factors for women. The source of covariation between aggression and political choices also differed between the sexes. A combination of genetic and environmental factors accounted for most of the cross‐trait correlations among males, whereas common and unique environmental factors accounted for most of the cross‐trait correlations among females. We consider the implications of our results for understanding how trait measures of aggression are associated with foreign policy and moral choices, providing evidence for why and how individuals differ in responding to complex social dilemmas. Aggr. Behav. 43:37–46, 2017. © 2016 Wiley Periodicals, Inc.