In this paper, the effect of adding nanoparticles on the performance characteristics of diesel engine was investigated. Up to now, several metallic nanoadditives including cerium and aluminum have been applied in this area. However, the possibility of using some other metals or modification in the additive structures as well as improving or changing the basic fluid is among factors manifesting a broad scope of work in this area. For this purpose, the silver nanoparticles were used as additives to the net diesel fuel. The results are indicative of significant alteration in the engine power, oil temperature, and the proportion of the released pollutants. The presence of the metallic nanoparticles inside the combustion chamber augments the heat transfer to fuel and shortens the ignition delay through an acceleration of the burning process. Meanwhile, these particles can aid fuel particles further penetrate in the compressed air during the spraying stage. Having all of these features altogether will improve combustion and hence the unburned carbons and other pollutants will decrease. Based on these observations, the rate of CO and NOx would be reduced significantly up to 20.5 and 13 %, respectively, noting that the net diesel and HC would undergo the highest change (up to 28 %). The results also indicate a 3 % fuel consumption reduction accompanied with 6 % improvement in the engine power, utilizing nanoparticles in most cases.