This study examined the effectiveness of internal control system, management support, and audit professionalism on internal audit effectiveness of local government. The sample consists of 39 regional inspectorates of six provinces in Indonesia. By using multiple regressions, this study found that internal control system and management support has positive impact on the effectiveness of the internal audit. However, there is no support for the audit professionalism on internal audit effectiveness. This study enriches existing research related to the effectiveness of the internal audit and emphasis the importance of internal control systems in local government