Background (Background, Rationale, Prior Research, and/or Theory): Parents' structure and participate in daily activities with their children in ways that resonate with their cultural beliefs known as parental ethnotheories. Healthy eating is a daily activity that can be shaped by parental ethnotheories. Objective: To understand parental ethnotheories (i.e. cultural beliefs) that support preschool-age (3–5 years) children's healthy eating guided by the three components of the developmental niche theoretical framework: physical and social settings of everyday routines, customs of childrearing practices, and parental ethnotheories. Study Design, Setting, Participants, Intervention: Utilizing hermeneutic phenomenology design, one-on-one interviews were conducted with 20 primary caregivers of preschool-age children until data saturation. Participants were selected using purposive sampling. Outcome Measures and Analysis: Data was analyzed using MaxQDA to develop codes and themes about parental ethnotheories that support preschool-age children's healthy eating. Results: Three overarching themes and related sub-themes emerged. Theme 1 was parental ethnotheories about the meaning of healthy eating included subthemes around participants' definitions of healthy eating, motivations to support children's healthy eating, and sources of knowledge about healthy eating. Theme 2 was parental ethnotheories that supported organization of children's physical and social settings included a structured mealtime routine and participants' food socialization strategies. Theme 3 was parental ethnotheories that supported children's learning about healthy eating included parent-child communication and engagement in age appropriate food activities such as meal preparation, visiting farmer's market, grocery shopping, gardening, cooking, and baking. Conclusions and Implications: Developmental niche of preschool-age children constitutes an interactive system (i.e. physical and social settings, childrearing practices, and parental ethnotheories) in which ethnotheories serve as guides to parenting practices where healthy eating messages are conveyed and practiced. Primary caregivers' knowledge/skills about healthy foods and positive feeding practices are important. Findings make an important contribution to the scant literature on parental ethnotheories that support preschool-age children's healthy eating, thus, presenting a unique qualitative contribution to the field of parenting/cultural food environment research. Funding: USDA-AFRI.