In this study we explored the development of children's beliefs about the concept of prayer. Three- to 8-year-old children were given a combination of tasks and structured interview questions designed to assess a number of basic aspects of their concepts of prayer. We also considered potential relations between children's concepts of prayer and two other explanatory systems — naïve psychology and magic — by probing understanding of the roles of knowledge and thinking in prayer and by comparing beliefs in prayer to beliefs in wishing. Results revealed significantly more sophisticated concepts of prayer than found in previous studies, including an earlier understanding of its mentalistic nature. We propose a new developmental trajectory for children's understanding of prayer and discuss interrelations between children's religious beliefs and their developing ontologies.