Abstract: Background and Objective: Converting waste cooking oils to biodiesel with favorable environmental implications is a major route to sustainable energy, pollution control and quality biodiesel production. Methodology: This study investigates the trans-esterification of Waste Groundnut Oil (WGO), Soybean Oil (WSO) and Waste Palm Kernel Oil (WPKO) catalyzed with potassium hydroxide (KOH). Results: Evaluating with ASTM standards, WGO, WSO and WPKO biodiesel generated were of good quality. The optimal conditions for biodiesel yielded are 10.67 methanol per oil mole ratio, 0.86 w/w oil catalyst concentration, 60°C reaction temperature and 71 min reaction time for WGO, 9.76 methanol per oil mole ratio, 1.04 w/w oil catalyst concentration, 60°C reaction temperature and 70 min reaction time for WSO and 9.51 methanol per oil mole ratio, 1.24 w/w oil catalyst concentration, 62°C reaction temperature and 80 min reaction time for WPKO. Conclusion: Waste cooking oils constitute ready feedstock for high volume, good quality and sustainable production of biodiesel as well as a realistic means of eliminating the pollution resulting from the indiscriminate disposal of waste oils common to both household and industrial users.