Cultural psychology has raised awareness of religiosity, spirituality, and secularism in people’s psychological lives. This article takes a cultural-developmental approach by examining the development of religiosity, spirituality, and secularism among culturally diverse adolescents. At the outset, an explanation is provided as to why the valid study of peoples’ psychological lives necessitates taking culture into account, and of key implications for theory and methodology. Throughout research on adolescent religiosity, spirituality, and secularism is described, including studies on conceptions of God, afterlife beliefs, the development of an Ethic of Divinity in moral reasoning, recent increases in spirituality and secularism, and the impact of globalization on worldviews and religiously-based puberty rituals. While the focus is on adolescents, the article includes relevant research with children and emerging adults. Concrete future research directions are proposed, including a call to address the extent to which effects of religion on adolescents are dependent on culture and globalization.