Purpose: A significant research base has increasingly shown that one of the most important factors affecting student achievement in second language classrooms is the teacher. Consequently, over the recent decades, much attention has been paid to teacher-related variables in research. Nevertheless, few studies have dealt with the relationship between teachers' self-efficacy, metacognitive awareness and their professional development in the context of English as a foreign language (EFL). As such, the objective of this study is to test a path analysis model of the variables and specifically to examine the hypothesis that metacognitive awareness mediates the relationship between self-efficacy and professional development. Design/methodology/approach: A quantitative correlational design was utilized to validate the research hypothesis. Then, data from 200 EFL teachers who were selected through available sampling was obtained using three questionnaires, namely metacognitive inventory by Cem Balcikanli, self-efficacy scale by Tschannen-Moran and Hoy and teachers' professional development inventory by Soodmand Afshar "et al." The Pearson correlation coefficient of self-efficacy (r = 757, p < 0.000) revealed a significant positive relationship with metacognitive awareness, and the Pearson correlation coefficient of metacognitive awareness (r = 0.848, p < 0.000) showed a significant positive relationship with professional development. Findings: The results showed the hypothetical model of the relationship among the research variables as well as verifying the mediator role of metacognitive awareness by multiple regression and path analysis. Then, the implications of metacognitive awareness, self-efficacy and professional development were put forward. Originality/value: The majority of research on teacher professional development has focused appropriately on its relationship with components such as management training, teacher practice, reflective practice and academic achievement. In this line of research, the investigation of the potential links among self-efficacy, professional development and metacognitive awareness as interacting variables is scarce. More substantially, no prior exploration has been conducted concerning the mediating effect of metacognitive awareness in association with English teachers' self-efficacy and professional development.