Portfolio management in Nigeria’s upstream oil and gas industry is critical for optimizing asset performance, mitigating operational and financial risks, and ensuring long-term profitability. Given the capital-intensive and high-risk nature of upstream petroleum operations, a structured framework integrating asset allocation, diversification, risk governance, performance monitoring, and investment screening is essential. This study examines portfolio management practices within Nigeria’s upstream sector, with emphasis on economic feasibility evaluation tools including Net Present Value (NPV), Internal Rate of Return (IRR), Payback Period, Profitability Index, and Break-even Oil Price analysis. The study further analyses key portfolio components such as goal setting, action planning, capital allocation, rebalancing, reporting, and risk management within the context of Nigeria’s regulatory and fiscal environment. The findings highlight the importance of integrated financial and strategic decision-making in enhancing investment resilience, optimizing resource utilization, and promoting sustainable sector growth. The study provides a practical framework for policymakers, regulators, and upstream operators seeking to strengthen portfolio performance in a volatile energy market.