This study examines the determinants of yield gap in rain fed and irrigated rice production systems in Kwara state, Nigeria. The objectives of the research are to; estimate the Profitability of rice production under rain fed and irrigated rice production systems; determine the technical efficiency of the farmers and to assess the determinants of yield gap in both production systems. These objectives were analyzed using: Gross Margin Budgetary analysis, Stochastic Frontier and Linear Regression Model respectively. The result shows that the gross margin for rain fed production system is ₦28,147.88 per hectare while, that of irrigated rice production system is ₦45,944.91 per hectare. The technical efficiency of rain fed rice production in the study area is 0.830 while that of irrigated rice production is 0.927. The determinants of yield gap in rain fed rice production system are: household size, family labour usage, urea fertilizer usage, farm size and variety of seed planted. The determinants of yield gap in irrigated rice production system are: farming experience, membership of association, farm size, and variety of seed planted. It was concluded that rice production in the study area is more profitable under the irrigated rice production system than the rain fed production system. This research therefore recommends that irrigation facilities and farm inputs (urea fertilizer, improved rice variety) should be made available to farmers as and when due.