In this study, waste cooking oil biodiesel was mixed with titanium dioxide (TiO2), a metal-based nano particle, and n-butanol (C4H9OH) along with euro diesel to examine their effects on diesel engines. Various ratio of fuel blends were prepared with TiO2 nano particles-diesel-biodiesel and n-butanol. The tests fuels were euro diesel (D100), biodiesel (B100), B20, B20 + TiO2, B20But10 and B20But10 + TiO2, respectively. Thermo-physical properties such as density, pour point, cloud point, cold filter clogging point, flash point and kinematic viscosity of all test fuels were determined followed by investigating engine performance parameters such as torque, power, fuel consumption and etc. Combustion analysis was also investigated. In addition, the effects on emissions such as CO, CO2, HC, NO and smoke opacity were also carried out. The addition of n-butanol to the fuel blends substantially affected density, kinematic viscosity and cold flow properties, while the addition of TiO2 has not much effect on these properties. For all tested fuels, the maximum brake engine torque and power were recorded at approximately 1400 rpm and 2800 rpm, respectively. The addition of TiO2 increased the brake engine torque and power 10.20% and 9.74% and decreased the brake specific fuel consumption 27.73% and 28.37%, respectively compared to blends without TiO2 additive. TiO2 additive increases the maximum cylinder pressure and heat release rate, as a result improved the engine performance and combustion. The addition of n-butanol in the fuel blend increased the maximum cylinder pressure and heat release rate values in comparison to euro diesel. The results of exhaust emission showed a decrease in CO, HC and smoke opacity emissions, whereas increased CO2 and NO emission, except the use of n-butanol reduced the values of NO emission, in comparison to euro diesel and without TiO2 additive. The results show that biodiesel produced from waste cooking oil, n-butanol and TiO2 additive can be used in diesel engines at certain proportion and that the additive materials improve the combustion characteristics, engine performance and exhaust gas emission.