Despite abundant renewable energy resources, Nigeria's transition toward clean energy remains slow and uneven. This study investigates the key challenges and opportunities shaping renewable energy integration in Nigeria through a mixed-methods approach combining policy analysis, stakeholder interviews, and survey data. National renewable energy policies implementation frameworks, and programme reports were systematically analysed alongside survey responses (n=200, 72% response rate) and semistructured interviews with policymakers, private-sector actors, and development partners (n=10). The findings show strong consensus among respondents that high upfront capital costs (78%), policy inconsistency (69%), financing constraints (65%), and weak regulatory enforcement (54%) constitute the most significant barriers to renewable energy scale-up. Over three-quarters of survey respondents identified capital cost as a significant constraint, while fewer than one-third expressed confidence in existing institutional capacity. Conversely, the study identifies substantial opportunities arising from Nigeria's solar resource endowment, growing privatesector participation, donor support, and emerging public-private partnership models. The analysis demonstrates that Nigeria's renewable energy challenge is fundamentally institutional rather than technological. Addressing governance weaknesses, stabilising policy frameworks, expanding concessional financing, and strengthening monitoring and accountability mechanisms are critical for unlocking renewable energy potential. The study contributes policy-relevant insights for accelerating renewable energy deployment in Nigeria and comparable petroleum-dependent developing economies