We review and discuss the evolutionary psychological literature on violence, homicide, and war in humans and nonhumans, and in doing so argue that an evolutionary perspective can substantially enhance our understanding of these behaviors. We provide a brief primer on evolutionary psychology, describing the basic tenets of the field. The theories of sexual selection and parental investment are explained and subsequently used to highlight the evolutionary logic underlying the use of violence by humans and other animals. Our examination of violent behavior begins with a focus on nonhuman animals, reviewing the different contexts in which violence occurs and discussing how an evolutionary perspective can explain why it occurs in these contexts. We then examine violence in humans and illustrate the similarities and differences between human and nonhuman violence. Finally, we summarize what an evolutionary perspective can offer in terms of understanding violence, homicide, and war, and discuss directions for future research.