Ethnotheories are beliefs that adults hold about children and the factors that impact upon their development. Scholars suggest that “ethnotheories” serve as cultural models that underlie motivations for parenting practices and the way adults organize children’s early experiences. This study examines Mexican adults’ ethnotheories about children’s health in two communities that are linked by transnational migrants and serve as sending and receiving communities for workers. Forty-four Mexican adults in six focus groups discussed well-being issues affecting children in their communities. Qualitative analyses using grounded theory revealed a complex conception of children’s health issues that included physical, psychological, and behavioral components and an interwoven system of causes with microlevel issues embedded in broader social, economic, and cultural contexts.