Abstract: In this study, fish oil was extracted from tilapia and mackerel viscera by the wet rendering extraction method. Using water base extraction method with more yield is a green chemistry which is better than using solvent extraction which is hazardous chemicals. The extracted fish oil is intended to be used for the production of biodiesel in further investigation. Increasing the temperature from 80ºC to 100ºC had significant effect on the extracted oil yield. Centrifugation had no significant effect on oil extraction at high cooking temperature (100 ºC) and therefore can be omitted from the extraction process. The results showed the applicability of producing fish oil from Tilapia viscera. The oil yield obtained from Tilapia viscera was about 20% which was higher than that obtained from Mackerel viscera (7% higher). Increasing cooking time in the range of 30 to 60 min had a significant effect on the extracted oil yield. 60 min cooking time was found to be optimum. The extracted fish oil was analyzed for its viscosity, moisture content, free fatty acids, acid value and fatty acids composition. The results indicated the suitability of fish oil for using for biodiesel production.