This study investigates the factors influencing internal audit effectiveness (IAE) within federal and regional governmental organizations in Jigjiga, Ethiopia. Despite the critical role of internal auditing in promoting transparency, accountability, and sound public financial management, the effectiveness of internal audit systems in Ethiopia's public sector remains inconsistent. The research examines five key determinants of IAE: internal auditor independence, management support, the relationship between internal and external auditors, auditor competence, and the use of information technology. A quantitative research approach was employed, using structured questionnaires administered to a sample of 81 participants selected through stratified random sampling. Data were analyzed using descriptive statistics and Ordinary Least Squares (OLS) regression. Findings reveal that all five factors have a statistically significant positive impact on internal audit effectiveness, with competence and management support being the most influential. The study contributes to both theory and practice by clarifying the key enablers of audit success and offering actionable recommendations for enhancing audit quality and public sector governance. The results are particularly relevant for policymakers, practitioners, and researchers seeking to improve internal audit practices in decentralized government structures.