Health promotion activities in secondary schools are scarce and have little involvement of the teaching staff. Most often, activities are developed from the curriculum that appears in school materials, with little capacity for adaptation and innovation. The aim of this study was to construct and validate a tool to find out teachers’ attitudes towards activities to promote healthy eating in secondary schools. For this purpose, a descriptive study was conducted. The total sample of the study consisted of 200 teachers from secondary schools. Internal consistency was determined by Cronbach’s alpha coefficient globally and by dimension, and with the corrected item–test correlation. The construct validity of the questionnaire was assessed by means of an exploratory factor analysis, for which the principal components method with Varimax rotation was used. A Likert-type scale with nine items and four response options about attitude was designed. The exploratory factor analysis showed a nine-factor solution, of which two had eigenvalues greater than 1. These two factors explained 63.4% of the variance. The Cronbach’s alpha internal consistency index obtained for the global scale was 0.81, and 0.75 and 0.85 for each component. The results obtained with this structure confirmed an adequate reliability and validity of the questionnaire.