An experimental investigation has been carried out to evaluate the effect of using diethyl ether as an additive to biodiesel on the combustion, performance, and emission characteristics in an unmodified diesel engine at different loads and constant engine speed. The results indicate that peak cylinder pressure and heat release rate is higher for 5% (by vol.) diethyl ether blended biodiesel than those of neat biodiesel. The carbon monoxide and smoke emissions decrease while oxides of nitrogen and hydrocarbon emissions increase for 5% diethyl ether blend than those of neat biodiesel. The brake thermal efficiency of 5% diethyl ether blend is higher as compared to biodiesel.