A field experiment was carried out during 2017 and 2018 summer seasons at Arab El-Awamer Station, Assiut, Egypt to study the response of two sorghum cultivars to foliar spray by different zinc oxide nanoparticles concentrations. The field experiment was carried out in a randomized complete block design using a strip plot arrangement with three replications. Zinc oxide nanoparticles (ZnO NPs) concentrations (control, 50, 100, 150 ppm) were allotted horizontally, while two genotypes of sorghum (Giza 15 and Dorado) were assigned vertically. The obtained results showed that plant height, panicle length, panicle width, 1000 kernel weight and grain yield / plant were affected highly significant or significant by different zinc oxide nanoparticles in the two growing seasons, except 50% flowering was insignificant in both seasons. Grain sorghum plants which were sprayed by 100 ppm ZnO NPs gave the highest mean values of grain yield /plant over both cultivars (44.87 and 44.90 g), as against (40.10 and 39.92 g) in control plants for the first and the second season, respectively. The same trend was observed for 1000-kernel weight, since the highest mean values of two cultivars obtained from plants which sprayed by 100 ppm ZnO Nps (32.23 and 32.55 g) with compared to control plants (28.25 and 28.45 g) for both seasons, respectively. The interaction between ZnO NPs concentrations and genotypes had a non significant effect on the all studied traits in the first season, while in the second season the interaction between ZnO NPs concentrations and genotypes had significant effects on plant height , panicle length, grain yield / plant and 1000 kernel weight.