The great changes in the business of economic units and the development of fraud and financial manipulation methods imposed on the internal audit great responsibilities and tasks of providing reliable information to the relevant parties with the speed and quality required, and this requires the development of this profession to keep pace with this development. Six Sigma is deemed as the most important methodology used to maintain quality and control performance. Hence, researchers have been deeply concerned with such subject which aims to identify the extent to which DMAIC Six Sigma Methodology can be applied to control the quality of internal audit performance. To attain such goal, the researchers applied realistic approach to accomplish this study. One of the more important results which have been concluded out of this study is that there is a manifest application of DMAIC methodology in Internal Audit Units through the application of the methodological stages (Define, Measurement, Analysis, Improvement and Control). Important recommendations were suggested in this respect the most important of which is that" High Management is taking pains to adopt the application of DMAIC SS methodology to attain performance quality especially in internal audit and support of work environment with quality concepts applied in the unit ".