Research on the internal audit function is relevant for improving the quality of governance in organizations. The internal auditor is an important element of government management in the context of realizing good governance by providing quality and effective audit results. The aim of this study is to examine the factors influencing (determinants) the effectiveness of the internal audit function in Indonesian local government organizations. The research samples were 137 respondents. This study used primary data in the form of a questionnaire. The hypothesis testing technique used Partial Least Squares-Structural Equation Modelling (PLSSEM) analysis. The results of statistical tests showed that independence, competence, and management support could increase the effectiveness of the internal audit function. However, this cooperative relationship does not moderate the influence of competence and management support on the effectiveness of internal audit. The practical implication of this study is that in order to increase the effectiveness of internal audit, internal auditors must uphold an attitude of independence, objectivity and freedom from conflicts of interest in carrying out their professional responsibilities. The practical value of this study also shows that to increase the effectiveness of public sector internal audit, internal and external auditors must increase cooperation to improve the effectiveness of internal audit,especially in discussion activities between internal and external auditors, communication between internal and external auditors, andactivities to share working papers between internal and external auditors.