This study empirically examines the impact of Foreign Direct Investment (FDI) on Nigerian economic growth for the period 1981–2018. The objectives were to examine the joint impact of FDI, exports (EXP), and the official exchange rate (EXR) on real Gross Domestic Product (RGDP). A cross-sectional time-series design was adopted, utilizing secondary data sourced from the Central Bank of Nigeria Statistical Bulletin, the International Monetary Fund, and the World Bank Database. The Ordinary Least Squares (OLS) multiple regression technique was employed alongside Augmented Dickey–Fuller (ADF) unit root tests, Augmented Engle–Granger (AEG) co-integration analysis, and an Error Correction Model (ECM) to capture both short-run dynamics and long-run equilibrium relationships. Results confirmed that all variables are integrated of order one, I(1), and are co-integrated, establishing a long-run equilibrium relationship among RGDP, FDI, EXP, and EXR. The regression R² of 0.61 indicates that the explanatory variables account for 61% of variation in RGDP. All three regressors — exchange rate, exports, and FDI — exerted positive and statistically significant effects on RGDP. The ECM coefficient of ?0.786 confirms rapid adjustment to long-run equilibrium, with 79% of disequilibrium corrected within one period. The results validate the Endogenous Growth Hypothesis and support the Export-Led Growth thesis for Nigeria. Policy recommendations focus on exchange-rate stability, economic diversification, infrastructure investment, anti-corruption measures, and targeted investment-promotion strategies to attract high-quality, long-term FDI inflows.