BackgroundIntersectoral collaboration, known to promote more sustainable change within communities, will be examined in an oral health promotion program (OHPP). In Peru, an OHPP was implemented by the Ministry of Health, to reduce the incidence of caries in schoolchildren. In rural Andean communities, however, these initiatives achieved limited success. The objectives of this project are: (1) to understand the context and the underlying mechanisms associated with Peruvian OHPP's current effects among school children living in rural Andean communities and (2) to validate a theory explaining how and under which circumstances OHP intersectoral interventions on schoolchildren living in rural Andean communities produce their effects.Methods and analysisThrough a realist evaluation, the context, underlying mechanisms and programme outcomes will be identified. This process will involve five different steps. In the first and second steps, a logic model and an initial theory are developed. In the third step, data collection will permit measurement of the OHHP's outcomes with quantitative data, and exploration of the elements of context and the mechanisms with qualitative data. In the fourth and fifth steps, iterative data analysis and a validation process will allow the identification of Context-Mechanism-Outcome configuration, and validate or refine the initial theory.Ethics and disseminationThis research project has received approval from the Comité d’éthique de la recherche en santé chez l'humain du Centre hospitalier universitaire de Sherbrooke. The initial theory and research results will be published in relevant journals in public health and oral health. They will also be presented at realist evaluation and health promotion international conferences.