Develop and validate the questionnaire to measure health education competencies of nurses. Methods: A cross-sectional descriptive study was conducted using qualitative and quantitative methods. The research was carried out in 2 phases, in which Phase I developed the questionnaire (Define the concept and content of the items to be measured; Build the initial questionnaire through consulting the experts); Phase II conducted the validity and reliability of the questionnaire (Investigate and test with the nurses; Test the validity; Test the reliability). Results: The structure of a questionnaire was determined to measure health education in 3 areas of knowledge, skills, and attitudes with 53 categories. The questionnaire was builded by consultation with 9 experts. Two categories (I-CVI scores < 0.78) were removed, forming an initial questionnaire with 51 items. The questionnaire was investigated and tested on 150 nurses. The rotating factor analysis gave results consistent with 45 categories in 3 areas of knowledge (2 categories - 15 items), skills (3 categories - 22 items), attitude (1 component - 8 items), explaining the variation of 62.61%, 64.48% and 82.07%, respectively. The group of nurses trained in health education had higher knowledge, skills and attitudes than the untrained group (p<0.05), the nurse group with long-term working experience had a higher score of knowledge, skills and attitude than the new group of nurses with (p<0.01). The intrinsic reliability of the questionnaire is evaluated well with the Cronbach alpha value of each component and the whole scale from 0.84 to 0.95; Reliability was repeated through a re-test of 35 nurses, and the ICC correlation coefficient was from 0.97 to 0.99. Conclusion: The health education competency questionnaire has been developed as a reliable and valuable measurement, may assist nursing educators and researchers in assessing the health education competence of nurses during clinical training