Despite the accumulated body of research on teachers' professional development few have offered a relationship between professional development and knowledge sharing or reflective practice. We investigated whether Iranian Teaching English as a foreign language (TEFL) teachers' reflective teaching and their knowledge sharing can predict their professional success. To answer the research questions a quantitative approach was utilized. Then, 264 faculty members through available sampling were recruited using three questionnaires, namely reflective teaching measurement scale by Akbari et al. (System, 38(2): 211-227, 2010), teacher professional development scale by Soodmand Afshar and Ghasemi (J Teach Lang Skills 37: 169-210, 2018), and Teachers' knowledge sharing behavior by Ramayah et al. (Eval Rev 38(2): 1-28, 2014). Findings showed that knowledge sharing has a significant relationship with professional development (P < 0.001). In addition, teachers' reflective practice has a significant relationship with professional development (P < 0.001). Based on the findings we suggest that TEFL teachers should promote their knowledge sharing and reflection to improve their professional development.