Migration may lead to changing power dynamics between parents and children in families. Children may change their behavior in order to exercise agency to respond to migration of family members or themselves. This systematic review seeks to understand how children exercise agency within families in the context of migration. The authors searched ten databases to collect English-written articles published in academic journals in or after 2010. The studies were coded to generate a quality indicator. 65 Articles with moderate and strong quality were included in this review, including 41 qualitative studies, 16 quantitative studies, and 8 mixed-methods studies. Children and adolescents with demographically and culturally diverse backgrounds were analyzed in these studies. The systematic review shows that children have different levels of behavioral agency in the migration decision-making process; they also exercise agency in different aspects of family life. For example, left-behind children exercise agency in care provision and information nondisclosure, and migrant children in media and language brokering. Children’s behavioral agency is place-specific. Adults working with children need to pay more attention to children’s behavioral agency in order to support children’s healthy development and facilitate their adaptation in the context of migration.