Diesel engines have a broader application area and have a significant share in the transportation sector. Although there are restrictions on producing within the scope of emission standards, diesel fuel will remain important in heavy-duty vehicles for some time. Therefore, studies continue for environmentally friendly combustion and low emissions in diesel fuel. This paper reveals the results of using nanoparticle fuel with natural gas (NG) on diesel engine emissions and performance. In the experiments, the motor load was adjusted from no to full load by increasing it at 25% intervals. Three different diesel-nanoparticle blends containing 25 ppm, 50 ppm and 75 ppm carbon nanotube (CNT) were prepared and each of these blends was tested both with and without NG. In light of the test results, it has been seen that the D75ppmCNT + NG mixture is the best fuel mixture compared to both diesel and nanoparticle-added diesel since it provides the highest value in brake thermal efficiency (BTE) and the lowest value in brake specific fuel consumption (BSFC) at full load conditions. In the case of using a D75ppmCNT mixture, around 29% decrease in BSFC and about 28% increase in BTE were observed according to the diesel fuel use. In terms of emissions, when NG is added to the D + CNT fuel mixtures, there is an increment in CO and HC emissions and a slight reduction in NOx emissions at low and medium load.