Background <p>Provision of government subsidized school meals at no charge to all students in income-eligible schools (Universal School Meals) is a critical policy approach to address food insecurity and risk for obesity in school-aged children. However, despite documented benefits, implementation challenges remain, which limit the uptake and associated impact of this provision. To ensure the longevity of this policy approach, equity-focused solutions that center the needs of those tasked with implementation and the most vulnerable Universal School Meals recipients are necessary. The aims of this study are to develop equity-focused implementation strategies and test them through a hybrid type III cluster-randomized trial to examine potential effectiveness on improving student uptake and implementation across the school system.</p> Methods <p>Aim 1 will comprise the first tasks of Implementation Mapping to co-develop implementation strategies in partnership with school implementers and recipients to ensure contextual fit within their school system. Aim 2 will comprise the final step of implementation mapping with a hybrid type III implementation-effectiveness trial to examine primary implementation and effectiveness outcomes of the applied strategies. Reach and penetration will be the primary implementation outcomes in addition to acceptability, feasibility, cost, and sustainability. Health outcomes comprise family food security, student dietary behaviors, and body mass index. Baseline, 6-month, and 12-month assessments will be recorded. A convergent (Quantitative–Qualitative) mixed methods design will be employed for analysis; exploratory hierarchical multiple regression models will be run for each behavioral outcome using students as the unit of observation and schools as the unit of analysis. Survey and interview data for implementation outcomes will be analyzed deductively according to the Exploration, Preparation, Implementation, and Sustainment and Getting to Equity frameworks then inductively to generate overarching themes across the trial period.</p> Discussion <p>This implementation mapping process will yield equity-driven strategies, which can be successfully implemented in school settings to improve uptake of USM and reduce food insecurity and obesity-related disparities in high-risk youth. This study presents a rigorous and equity-driven implementation research agenda with the potential to advance school-based obesity prevention efforts by identifying, developing, and evaluating context-specific strategies that meet the needs of vulnerable student populations.</p> Trial registration <p>ClinicalTrials.gov, NCT06579079, Registered on 11–5-2024.</p>