Aging dam systems face increasing challenges associated with changing hydrologic conditions, environmental requirements, and regulatory expectations. This study presents a decision-making framework based on Multi-Criteria Decision Analysis (MCDA) and the Analytic Hierarchy Process (AHP) to assess long-term management alternatives for an aging earthfill dam within a highly interconnected watershed system. Four management strategies were evaluated: decommissioning, modification, replacement, and rehabilitation. The assessment considered dam safety, reservoir performance, hydraulic infrastructure, environmental effects, Indigenous and socio-economic considerations, downstream impacts, and long-term operational requirements. Evaluation criteria were aligned with key Canadian Dam Association (CDA) technical themes, including dam safety, climate resilience, environmental stewardship, and public safety. The AHP-based framework integrated engineering, environmental, operational, and economic considerations into a transparent and defensible evaluation. Results indicate that, in multi-reservoir and multi-structure systems, option selection cannot rely solely on structural or hydraulic performance. System-wide interactions, including flow redistribution, reservoir connectivity, downstream impacts, and infrastructure interdependencies, are critical to identifying the preferred alternative. The methodology provides a practical and transferable approach for supporting long-term dam management decisions under uncertainty.