This paper examines the determinants of internal audit effectiveness in decentralized local government administrative systems of Ghana. Ghana's local government system is structured into metropolitan, municipal, and district assemblies (MMDAs). For the purpose of the study, we focused on the Ashanti region of Ghana which has the highest number of MMDAs. The motivation for the study is derived from the increased interest in the internal audits of local government units. Using a descriptive survey, the data gathered, through the use of questionnaire, revealed that majority of the internal audit staff of MMDAs in the Ashanti Region of Ghana possess the requisite professional proficiency. Contrary to the perception that audit quality in the public sector is usually compromised, the study revealed that there exists high quality of audit work due to compliance with the international standards on auditing and local audit legislations. Professional proficiency, organizational independence, and career advancement were found to have statistically significant positive relationship with internal audit effectiveness, whiles top management support was found to have no effect on internal audit effectiveness.