The effectiveness of Regional House of Representatives (DPRD) oversight of the Regional Revenue and Expenditure Budget (APBD) is essential to ensure that public funds are managed transparently, accountably, and in accordance with regional development priorities. Although previous studies have examined the oversight function of local legislatures, empirical studies that integrate institutional capacity and public participation in the oversight of APBD, particularly in smaller municipalities such as Pagar Alam City, remain limited. This study aims to analyze the effectiveness of APBD oversight by the Pagar Alam City DPRD by examining the institutional and participatory factors that constrain the implementation of its oversight function. The study employs a qualitative empirical approach based on document analysis, interviews, and participatory observation. The analysis is informed by the theories of checks and balances, good governance, Weberian bureaucracy, and public participation. The findings indicate that the effectiveness of DPRD oversight is constrained primarily by two interrelated patterns: limited institutional capacity and weak external accountability mechanisms. Limited technical competence in public finance, fragmented oversight among commissions, and the absence of standardized performance-based oversight procedures weaken the capacity of DPRD to evaluate budget implementation substantively. At the same time, limited public participation and suboptimal coordination with regional government agencies and internal oversight institutions reduce the flow of information required for effective legislative control. Political dynamics further complicate the independence of oversight. The study argues that strengthening APBD oversight requires not merely the expansion of formal legislative powers, but the development of institutional capacity, performance-based oversight procedures, meaningful public participation, and inter-institutional coordination. The findings contribute to the understanding of how checks and balances operate at the local level within the context of decentralized governance.Keywords: APBD; DPRD Oversight; Institutional Capacity; Public Participation; Good Governance.