Objective The aim of this research study was to identify the core competencies for health education teachers in supporting the development of health literacy among their students. Method/Results A three round Delphi method was employed. Experts in health education were asked to identify core competencies for school health educators. Twenty six participants from the academic field were invited to participate in the study. Twenty participants completed the first round of the Delphi, while eighteen took part in round two and fifteen participated in the final round. Data were collected using an electronic questionnaire. The first round contained an open ended question in which participants were asked to name and define all the competencies they perceived were important. Thematic analysis was undertaken on these data. A list of 36 competencies was created from this round. This list was then returned to the same participants and they were asked to rate each competency on a 7 point semantic differential scale in terms of importance. The resulting data were then analysed. For the final round, participants were presented with a list of 33 competencies and were asked to rank them again, in order of importance. Conclusion Twelve core competencies emerged from the analysis and these competencies comprised of a mixture of knowledge, attitude and skills. The authors suggest that how these competencies are achieved and operationalised in the school context can be quite complex and multi-faceted. While the authors do not seek to generalise from the study they suggest that these competencies are an important input for all stakeholders, in order to question national and international teacher guidelines. In addition the competencies identified may provide a useful starting point for others to undertake deeper analysis of what it means to be an effective health educator in schools.