This study experimentally investigates the effects of fuel additive on the exhaust emissions and performance of a marine diesel engine installed on a ferry. The fuel additive consisting of hydrocarbon solution of cyclic and aliphatic amino compounds is used to blend the ultra-low-sulfur diesel fuel. On-board measurements of NOx, SO2, CO2, CO, hydrocarbon and particulate matter emissions with and without fuel additive were carried out at different engine loads. The composition and formation of the particles are studied by using scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis. The results show that the fuel additive reduced the emissions of CO, hydrocarbon and particulate matter by 6.5%, 60% and 38%, respectively. The elemental analysis of particles indicates that there are 13 major elements such as C, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Zn and Fe in the samples. Considering the type of the fuel, the Ca, Fe and N are thought to come mainly from the fuel additive. The composition and components of the diesel particles and also the specific fuel oil consumption are not affected significantly by the fuel additive. Consequently, the fuel additive improves the combustion performance and reduces the CO, hydrocarbon and particulate matter emissions of the engine.