The actual yield of rice in Nigeria has not been able to reach its potential. Consequently, the cost of rice importation is alarming. However, rice yield varies under various production systems. Therefore, this study examines the determinants of yield gap in rainfed and irrigated rice production systems in Kwara state, Nigeria. Gross Margin Budgetary analysis, Stochastic Frontier, and Linear Regression Model were respectively used to estimate the profitability, technical efficiency, and determinants of yield gap in both production systems. The result shows that rice production is more profitable and efficient under the irrigated rice production system than the rainfed rice production system. It was also discovered that the significant determinants of yield gap in both production systems vary. However, the size of farm cultivated and the rice variety planted are common significant determinants of yield gap in both systems. This research therefore recommends that irrigation facilities and improved rice variety should be made available to farmers. Additionally, policy makers should formulate policies that would enable rice farmers to have access to larger farm lands.