Childhood unpredictability and harshness are associated with patterns of psychology and behavior that enable individuals to make the most of adverse environments. The current research assessed effects of childhood unpredictability and harshness on individual differences in sacrificial moral decision making. Six studies (N = 1,503) supported the hypothesis that childhood unpredictability, but not harshness, would be associated with fewer decisions to reject harm (consistent with deontological ethics) and to maximize overall outcomes (consistent with utilitarian ethics). These associations were not moderated by perceptions of current environmental unpredictability (Studies 3a and 3b) and were robust to potential confounds (religiosity, political conservativism, Big 5 personality traits, and social desirability; Study 5). The associations between childhood unpredictability and lower deontological and utilitarian tendencies were statistically mediated by low levels of empathic concern and poor-quality social relationships (Study 4). Findings are consistent with the possibility that early calibration to ecological unpredictability, but not harshness, undermines other-oriented psychological processes which, in turn, reduce moral concerns about harm and consequences for other people.