Background: Health promoting schools (HPS) is hypothesized to influence student health and wellbeing by promoting a 'school ethos' that shapes the physical environment, social relations, organisational structure, policies and practices within the school. This complex set of conceptual dimensions makes school ethos challenging to measure as an important context for the implementation of HPS. The purpose of this research was to develop and explore a comprehensive measure of health promoting school ethos (HPSE) for the evaluation of HPS implementation, student health and well-being. Methods: We used a multi-method, iterative process to identify relevant HPSE concepts through triangulation of conceptual literature, existing tools and the tacit knowledge of school stakeholders. The HPSE measurement tool was administered to 18 elementary schools through a principal and teacher survey and an environmental assessment, followed by the development of a total and dimensional HPSE scores for each school. Testing for internal consistency of items was used to examine theorised concepts and sub-scores across HPSE dimensions, and total scores are summarised. Results: HPSE included eight conceptual dimensions with internal consistency ranging from α = 0.60 to a = 0.87. Total HPSE scores across schools (N = 18) ranged from 1 to 8 (Mean = 3.94, SD = 2.1), with 28% to 65% of schools reporting 'high' on respective HPSE dimensions. Conclusions: The HPSE tool holds potential for the conceptualization of critical components of school context as it relates to HPS. DRAFT ABSTRACT Background: Health promoting schools (HPS) is hypothesized to influence student health and wellbeing by promoting a 'school ethos' that shapes the physical environment, social relations, organisational structure, policies and practices within the school. This complex set of conceptual dimensions makes school ethos challenging to measure as an important context for the implementation of HPS. The purpose of this research was to develop and explore a comprehensive measure of health promoting school ethos (HPSE) for the evaluation of HPS implementation, student health and well-being.