Given the special importance of medical professionalism, a successful faculty development strategy not only teaches professionalism in cognitive domain but also creates practical instructors who can act as role models for students. This study proposed to identify themes that can explain effective factors in teaching and learning professionalism among medical teachers. The study was qualitative. Twenty-four experts in medical education participated in the study from all medical universities of Iran. Data gathering was performed via semistructured interviews. Interviews were transcribed and analyzed by classic content analysis. At the end, the factors were confirmed by the focus group consisting of six experts. One hundred seventy-seven codes were extracted. Codes were categorized into 24 subcategories and five main categories: (1) culture, (2) educational factors, (3) background, (4) attitude, and (5) organizational factors. There are many effective factors for a proper faculty development in teaching and learning professionalism. These factors could be individualized, organizational, or external. We cannot design a program without considering these factors.