Although biodiesel has a promising potential to be used as an alternative fuel for compression-ignition engines, its use may deteriorate engine performance. The objective of the current study was to enhance the performance of a compression-ignition engine operated with a diesel-biodiesel blend using diethyl ether (DEE). Four fuels were examined in a diesel engine to assess its performance and analyze the combustion process. These fuels were diesel, biodiesel-diesel mixture, and two mixtures of biodiesel-diesel- DEE with DEE proportions of 5% and 10% by volume. It was found that using diesel-biodiesel blend increased the minimum brake specific fuel consumption (bsfc) and reduced the maximum thermal efficiency by 8.1% and 6.8%, respectively, compared to diesel fuel. However, employing 5% DEE in the dieselbiodiesel mixture improved engine performance considerably for most engine loads in comparison with all fuels. Altering the fuel type had no significant impact on combustion start instant. However, the heat release rate was lower and combustion duration was longer for diesel compared to other fuels at higher engine loads. Using DEE did not significantly affect engine stability.