{Reference Type}: Journal Article {Title}: Methodology for evaluation of complex school-based health promotion interventions. {Author}: O'Byrne Y;Dinneen J;Coppinger T; {Journal}: J Public Health Policy {Volume}: 0 {Issue}: 0 {Year}: 2024 Aug 12 {Factor}: 3.526 {DOI}: 10.1057/s41271-024-00510-4 {Abstract}: There is a need for careful examination of large volumes of collected (structured and unstructured) information related to school-based evaluation. There is also no published, comprehensive framework/s for evaluating complex interventions in Irish primary schools. The aim of this paper is to outline a methodology for process evaluation of an Irish primary school-based physical activity (PA) and nutrition intervention. Evaluation followed the three themes outlined by the British Medical Research Council: implementation, context, and mechanism of impact that we further divided into six dimensions. Methodological tools included questionnaires, PA logs, reflective journals, write and draw, and semi-structured interviews. We triangulated findings across these multiple tools to assess each dimension. We designed a unique framework to enable comparisons and offer researchers a template for evaluating complex health promotion interventions in primary schools. We present a methodology for evaluating a complex school-based health promotion intervention. The framework we propose integrates process and outcome data. It aims to enhance future result interpretation and facilitate informed comparisons among intervention schools.