Argemone mexicanamethyl ester was prepared by two steps. Transesterification process due to its high acid value was tested for its performance and emission analysis with variation of load and blends at a fixed compression ratio of 17.5. It has been found that at part load the brake thermal efficiency of B20 blend is higher than diesel and brake-specific fuel consumption decreases with load and increases with concentration of biodiesel in the blend. The exhaust gas temperature increases for increase in both load and concentration of blend. Carbon monoxide (CO) and hydrocarbon emissions were lower than standard diesel at the cost of nitrogen oxide (NOX) emissions.