Dental cement based on zinc phosphate (Zinc Phosphate Cement) is the oldest dental cement that is still widely used today. One disadvantage of zinc phosphate-based dental cement is its low mechanical properties. In this study, ZnO nanoparticles are added to the zinc phosphate dental cement with the hypothesis that there will be the strengthening of the mechanical properties of dental cement. The fraction of ZnO nanoparticles were variedly added from 0.1 g, 0.5 g, 1 g and 1.5 g to the zinc phosphate dental cement which is then compared to the dental cement without the addition of ZnO nanoparticles. The materials were manually mixed and mold to form dental cement pellets (4 mm thick and 4 mm in diameter). Characterization of pellet hardness and strength result in a linear value to the addition of ZnO nanoparticles in which the value of hardness and strength increases as increasing of ZnO nanoparticles fractions. XRD analysis results indicate the appearance of peaks Zn3(PO4)2.4H2O and ZnO compounds supported by the analysis of surface structure using SEM. The resulting dental cements have an increased value of hardness and compressive strength due to the improvement of its micro structure having a small amount of crack and a homogeneous distribution of nano ZnO. Through this phenomenon, it can be concluded that the addition of nano-ZnO can be applied to increase the value of hardness and strength in dental cement.