This Element provides a comprehensive yet concise account of scientific research on children's religious and spiritual (RS) development. After providing a historical sketch of definitional issues in the science of RS, the first section reviews basic descriptive information on children's RS development as well as wholistic theoretical models and measures of children's RS development. The second section covers evidence about links of child and parental RS to children's psychosocial adjustment, and highlights the need for more research that discriminates specific positive and negative manifestations of RS for children's development. The third section summarizes evidence about the robust influence of parents on their children's RS development and parents' perceptions of their role in this process. The fourth section focuses on cognitive-developmental research on children's cognitions about God/deities and prayer. The Element concludes with a synopsis of key themes and challenges that researchers face to advance the science of children's RS development.