Background: The purpose of this study was to develop and test the psychometric properties of a questionnaire that assesses preschool teachers' self-efficacy in providing asthma care. Methods: A total of 407 teachers from 54 preschools in Taiwan participated in the study by completing the asthma management self-efficacy scale. We assessed validity of the scale through expert opinion, exploratory factor analysis, and confirmatory factor analysis. The reliability of the scale was assessed using Cronbach's alpha. Results: A 10-items questionnaire was developed to assess self-efficacy concerning asthma treatment. On the basis of explorative factor analysis, 2 major factors emerged from the 10 self-efficacy items that together explained 61.68% of the total variance in teachers' self-efficacy with regard to asthma care. We named these factors "prevention of an asthma episode" and "the treatment of an asthma exacerbation." Confirmatory factor analysis revealed that the 2-factor model provided the best goodness-of-fit. Conclusions: This scale could provide health professionals with useful information concerning preschool teachers' self-efficacy with respect to the management of asthma in the preschool setting.