According to the change in the role of internal auditors, new competencies are needed. The purpose of this research is development of internal audit managers’ competency model, with regard to contextual and environmental attributes and conditions surrounding the internal audit profession in Iran. With regard to exploratory approach of this research, and because of absence a comprehensive research to develop internal auditors’ competency model in prior researches; therefore, in this study, we used qualitative research method and grounded theory approach. To achieve this goal, with obtaining faculty and internal auditing experts insights through unstructured interviews, and analyzing the data by using the open coding, axial coding & selective coding approach and extracting major categories, categories, and subcategories (concepts), we developed internal auditors’ competency model in Iran, including causal conditions, intervening conditions, context, as well as action strategies related to internal auditors’ competency and their consequences. According to this model, internal auditor managers need a series of Individual, technical, managerial and environmental competencies to achieve the desired level of effectiveness. In fact, these findings show core competencies for Iranian internal audit managers which can be used as an indicator by students, internal auditors, professional body, and organizations to equip and evaluate competencies.