Purpose, this research investigates the relationship between internal audit functions and organizational performance. The research takes ministries in the Sultanate of Oman as a case study. The research provides an active role of decision-makers in ministries by providing authority, tools, facilities, and appropriate environment to internal audit units and how that will affect the performance of those ministries. Approach/ methodology is basic research. In order to achieve the study aims and objectives, a quantitative research approach is appropriate, thus the research uses a questionnaire method to collect data from ministries' auditors. The research uses the SPSS program to analyze the data collected by questionnaire. Result/ findings, there is a causal relationship between internal audit functions (independence, Competence, and size) and organizational performance, which is achieved through the authority and facilities given by decision-makers in government ministries. Practical implications and results encourage ministries in the Sultanate of Oman to focus on the issue of the effectiveness of internal audits and strengthen the internal audit units' capacity of ministries. Originality/value, the research would offer academic contributions to existing research on internal audit functions and their effects on organizational performance. The advanced quantitative data analysis used in this research will allow future researchers to explain the contribution of this research to understand the importance of internal audit functions (independence, competence, and size) on organizational performance. Keywords, internal audit functions, organizational performance, internal audit independence, internal audit competence, internal audit size.