The effectiveness of the internal audit function is essential to improve the performance of public sector by the way of the internal auditor's ability to detect and correct any defects and remain corrected. Thereby, this research aims is to examine the direct relations effects of competence of internal auditor, independence of internal auditor, and the effectiveness of internal control system towards the effectiveness of internal auditor in Malaysian Public Sector namely Malaysian Federal Statutory Bodies (MFSB). In addition, this study employed moderating variable (management support) to test the relationship between independent variables and dependent variable. The researcher adopted quantitative research method. This research paper was based on the pilot test that being conducted on 30 respondents where the questionnaires were distributed via respondent's electronic mail. The research findings revealed that the independence of internal auditor is the most important determinants of internal audit effectiveness. Besides, the interaction between management support and independence of internal auditor is also one of the important determinants of internal audit effectiveness in Malaysian Public Sector. As this research only employed a small number of respondent, further researcher should employed more respondent in their analysis to generate more reliable result.