This paper investigates the impact of the Organization of Petroleum Exporting Countries quota system on Nigeria’s crude oil output over the period 1999 to 2025. Major petroleum sector indicators such as Nigeria’s OPEC production quota, OPEC total production, quota compliance rate, and OPEC spare capacity, were employed as explanatory variables, while crude oil production served as the dependent variable. Secondary data were obtained from the National Bureau of Statistics, OPEC Annual Statistical Bulletin, OPEC Monthly Oil Market Report, and author’s computation (2026). To ensure analytical rigor, the Augmented Dickey-Fuller unit root test was utilized to examine the stationarity properties of the variables, while the Auto-Regressive Distributed Lag model was applied to estimate both short-run and long-run dynamics. The bounds testing approach confirms the existence of a long-run relationship between OPEC-related variables and Nigeria’s crude oil output. Empirical findings indicate that OPEC total production and OPEC spare capacity exert a negative and statistically significant influence on crude oil production, In contrast, the quota compliance rate exhibits a positive and significant relationship with crude oil production, and However, Nigeria’s OPEC production quota is found to have a negative and insignificant effect on crude oil production in Nigeria The study concludes that while OPEC mechanisms play a critical role in shaping Nigeria’s oil output, their effectiveness is largely conditioned by domestic production capacity and operational efficiency. It therefore recommends that policy efforts be directed toward aligning quota levels with domestic capacity through sustained investment in infrastructure and improved operational performance.