In this study, production of biodiesel from new and used palm and soybean oils was carried out using a transesterification method. The effect of catalyst amount used towards the percentage yield, soap content and heat of combustion of the biodiesel produced was investigated. The soap content and heat combustion of the biodiesel were determined using titration (AOCS Cc-95) and heat calorimeter bomb (ASTM D240-09), respectively. The results showed that catalyst concentration of 0.5 w/w% gave the best result in terms of yield of biodiesel produced from both palm and soybean oils. However, the quality of biodiesel (i.e. soap content and heat of combustion) produced from palm and soybean oils behaved differently towards catalyst concentration. Overall, both oils (palm and soybean), either new or used oil apparently showed no significant difference in term of yield or qualities of biodiesel produced. This indicates that the used oil has high potential as an economical and practical future source of biodiesel.