Latino preschool children are more obese than preschool children in other racial/ethnic groups. Few family- based obesity interventions exist that target Latino preschool children and use culturally-appropriate measures and approaches. Latino peer health educators (promotoras) have been effective in increasing knowledge and promoting behavior change in Latino populations; however, to date, no promotora-led child obesity interventions targeting Latino preschool children exist. The purpose of the proposed research is to develop and evaluate the feasibility and effectiveness of a family-based, promotora-mediated child obesity intervention. The proposed study will employ a mixed methods sequential research design, organized into two major phases: Phase I: Conduct language-stratified focus groups and cognitive interviews with Latino parents of preschool children to inform the development of a culturally-appropriate intervention and measures; Phase II: Test the feasibility and effectiveness of the intervention; Thirty Latino parents of children aed 2-5 years (Phase I) and fifty parent-child dyads (Phase II) will be recruited from Newberry and Saluda counties, South Carolina by six promotoras (females >18 years, active in community) from their own networks of churches, schools, neighborhoods, and corner stores. Promotoras will be recruited upon completion of the Promotores Initiative training program at the University of South Carolina and will receive an additional 20 hours of training using the intervention curriculum finalized after Phase I; promotoras will then deliver the home-based intervention to families over 10, 90-minute weekly sessions. The sessions, organized into education, practice and action (i.e., goal setting) components and inclusive of all family members who desire to attend, will educate and train parents to set feasible goals related to family diet, physical activty, and sedentary behavior to create supportive home environments to promote a healthy weight in their children. Primary outcomes (i.e., child body mass index [BMI] z-score and percentile) and secondary outcomes (e.g., child diet [food screener] and physical activity [accelerometry], the physical and social home environment [parent survey]) will be assessed pre- and post-intervention. Process evaluation will assess fidelity, dose, reach, recruitment, and contextual factors using multiple data sources and mixed methods. Descriptive analyses based on process data from promotoras, parents, and audio recordings will be used to determine intervention feasibility and level of implementation. Intervention impact on primary and secondary outcomes controlling for relevant variables will be assessed with ANCOVA in SAS. The proposed research carries high public health significance because it will influence specific behaviors in parents and children that have been associated with excessive weight gain. The research is innovative because it will be the first to use promotoras in a child obesity intervention for Latino preschool age children. If successful, this approach will be evaluated in a large-scale intervention and provide a potential model to help to address and prevent child obesity in Latino families.