Background: Previous research has revealed that teaching self-efficacy could play a critical role in engaging students in integrated STEM education; however, teachers' multiple identities in STEM education (i.e. implementers, disseminators, and designers) and their commitment with respect to the different identities have not been considered and examined. Purpose: This study aimed to investigate STEM teachers' self-efficacy and commitment as implementers, disseminators, and designers, and to explore the relationships between teachers' self-efficacy and commitment with respect to the three identities. Sample: 629 secondary STEM teachers completed a questionnaire that included the items of teachers' background information and 46 items to measure their self-efficacy and commitment with respect to the three identities. Methods: To compare the differences in teacher self-efficacy and commitment with respect to the three identities, repeated measures analyses of variance were used. A mixed-model analysis was conducted to examine the effects of both identity and experience with self-efficacy as a covariate on teacher commitment. Also, the structural equation modelling (SEM) method was employed to investigate the structural relationships within and between teacher self-efficacy and commitment with respect to the three identities. Results: The results indicated that STEM teachers' self-efficacy and commitment were influenced by their identities as well as their STEM teaching experience. STEM teachers' self-efficacy and commitment to being implementers and designers were significantly higher than their self-efficacy and commitment to being disseminators. Additionally, the results of structural equation modelling indicated that teachers' self-efficacy for the three identities was highly related, as was their commitment to the three identities. Self-efficacy of being disseminators had the largest impact on teacher commitment to being disseminators, designers and implementers. Conclusion: The results highlight the importance of researching STEM teachers' multiple identities, and suggest that STEM teachers' different identities lead to different levels of self-efficacy and commitment.