The increase in crude oil prices, the problems associated with long term availability of conventional hydrocarbon fuels for automotive engines, and the continuous emission of combustion pollutants into the environment are cause for concern. These challenges have necessitated the need to investigate the performance of Jatropha curcas oil methyl ester as diesel fuel extender in compression ignition engines. A test rig of 2.43 kW, 165 F single cylinder -four stroke variable speed direct injection engine, and incorporated with a 1.25kVA Honda E 1500 A.C dynamometer manufactured by Ningbo Tri-circle Power Machinery Company, China and Honda Company, Japan, was used to conduct the engine performance tests on samples of fossil diesel fuel (DF), and diesel fuel containing 5%, 10%, 15%, and 20% by volume of Jatropha curcas oil methyl ester (i.e. B5, B10, B15, and B20 DF-JME blends) respectively. At maximum engine speed of 2600rpm, the brake power and brake mean effective pressure generated by DF-JME blends are somewhat comparable to fossil DF, with B10 and B20 samples exhibiting least engine power by the order of 1.80% and 2.72%. In terms of fuel consumption, B5, B10, B15 and B20 DF-JME blends are 1.63%, 3.06%, 0.030% and 0.514% higher than fossil DF. However, the lower break thermal efficiency could be attributed to the slow progress of combustion, lower heating value and combustion temperature of the DF-JME fuel mixture. Hence, it could be concluded from this study that transesterified Jatropha curcas oil is suitable for use as diesel fuel extender in compression ignition engines. To this effect, a deliberate investment in biodiesel production from Jatropha curcas oil will conserve crude oil reserve and improve Nigeria's energy security.