Psychological functions of religion in youth are discussed from a motivational and anthropological approach including a historical and cultural perspective. The role of religious beliefs in ancient, medieval, and traditional societies are described, referring to some possible origins in the evolution of such beliefs. These origins are seen in the belief in an invisible “other” (or spiritual) world, motivated to make sense of otherwise incomprehensible events. This is assumed to have strong psychological effects on the formation of religion in mankind, on the development of religious practices, and the role and importance of shamans and priests. The psychological functions of religion in adolescents’ development by initiation rites, and in modern societies with focus on natural sciences and a secularization of the worldview are discussed. There are a great variety of beliefs and strong differences in the importance of religion in different cultures. The importance and power of religion differ, ranging from fundamentalism to secularization. The importance of these differences for emergent adults are considered. Religiosity may foster identity development, civic engagement, prosocial activities, and life satisfaction. However, it can also promote other less desirable behaviors in youth like intolerance and aggressiveness against unbelievers. Both the cultural context and individual motivations are shown to affect religious development and personality development in adolescence in various ways.