The effect of biodiesel percentage in biodiesel-diesel blends on the engine under different engine operation conditions must be predicted to achieve high performance. The goal of the present paper was to model brake power, brake torque, thermal efficiency, and specific fuel consumption of a diesel engine fueled by algal biodiesel-diesel blends. The response surface methodology was successfully applied to model the performance indicators of biodiesel-diesel fueled OM 314 diesel engine at various engine loads and rotational speeds. Brake power, torque, and thermal efficiency increased by increasing engine load. Increasing engine rotational speed caused increase in brake power whereas highest brake torque and thermal efficiency was obtained in medium engine rotational speed. Increase of biodiesel percentage caused decrease in. Biodiesel had negative effects, but it had lower effects than engine load and rotational speed on the change of the engine performance indicators. Brake specific fuel consumption decreased by increasing load but it was lowest in medium rotational speeds. A quadratic model was suitably fitted to predict the effects of input-output variables with statistical significance of 1% probability level. The coefficient of determinations for prediction of the engine brake power, brake torque, thermal efficiency, and brake specific fuel consumption were 97.63, 99.74, 97.41, and 95.72%, respectively. The result of the present work is useful to find optimum biodiesel percentage and engine load and rotational speed to achieve high performance fuel blends.