This paper describes an experimental study of using jatropha oil as a fuel in diesel engine. In this study the effect of using Jatropha oil – plastic oil blends (JP10 JP20) on the engine performance, exhaust emission have been experimentally investigated. This present work deals with 10% Jatropha oil and 90% plastic oil called JP10, 20% Jatrophaoil and 80% plastic oil called JP20 were used in single cylinder four stroke, water cooled diesel engine. The experimental result showed that the carbon monoxide, hydrocarbons and exhaust gas temperature were significantly reduced. Oxides of nitrogen, Brake specific fuel consumption was increased and also brake thermal efficiency were found to have increased with Jatropha oil –plastic oil blends.