Historically, religion and religious belief have often been credited as the source of human morality. But what have been the real effects of religion on prosocial behavior? A review of the psychological literature reveals a complex relation between religious belief and moral action: leading to greater prosocial behavior in some contexts but not in others, and in some cases actually increasing antisocial behavior. In addition, different forms of religious belief are associated with different styles of co-operation. This body of evidence paints a somewhat messy picture of religious prosociality; however, recent examinations of the cognitive mechanisms of belief help to resolve apparent inconsistencies. In this article, we review evidence of two separate sources of religious prosociality: a religious principle associated with the protection of the religious group, and a supernatural principle associated with the belief in God, or other supernatural agents. These two principles emphasize different prosocial goals, and so have different effects on prosocial behavior depending on the target and context. A re-examination of the literature illustrates the independent influences of religious and supernatural principles on moral action.