The purpose of this study of factors affecting the internal audit effectiveness they face in their executionrnof duties in federal public bodies in Ethiopia particularly admin and general service sector. In line withrnthis, the main purpose of the paper is evaluation of effectiveness of internal auditing system in government organizations in Ethiopia, especially in 10 sample federal public bodies. For achieving this objective,rnboth primary and secondary data were drawn using questionnaires and interview and analyzed in thernmost appropriate techniques such as; frequency tables and percentages. The study revealed that therernwas problem of independency there was inadequate technical staff proficiency and absence of continuous professional training development programs for internal auditors and lack of sufficient number staff.rnFurthermore, auditee departments and the managements did not attention that the audit service canrnadd value to their activity and to the organization and they have not adequately supported the department. It was also evaluated that the scope of internal audit services is limited only to financial statementrnaudit and performance audit is overlooked. Therefore, there should be extending the scope of internalrnaudit services by including performance audit with appropriate increase technical proficiency of the internal audit staff; adequate independence to internal auditors; put into practice internal and externalrnaudit quality assurance and improvement programs, and alleviating other impeding factors related tornaudit execution in the organizations under study.