The objective of this study was to evaluate the effects of dietary supplementation with zinc oxide nanoparticles (ZnO-NPs) on the performance, egg quality, Zn retention, immunity responses, superoxide dismutase activity (SOD), egg malondialdehyde (MDA) content, and serum parameters in laying hens in the late phase of production. A total of 288 laying hens at 64weeks of age were randomly assigned to 4 treatments with 6 replicates, and 12 birds within each group. Experimental diets included a corn-soybean meal-based diet (without Zn supplementation) and a basal diet supplemented with 80mg/kg of Zn-oxide, ZnO-NPs, and Zn-methionine. The results indicated that egg production and egg mass were significantly higher in the Zn-methionine and ZnO-NPs groups (p<.05). Also, eggshell thickness and shell strength increased in the ZnO-NPs group as compared with the other groups (p<.05). Moreover, Zn supplementation decreased egg loss (p<.05). There were significant differences among treatments in Zn deposition in tibiotarsus, liver, pancreas, eggs, and excreta (p<.01). Antibody titre, heterophil (%(, and phytohemagglutinin (PHA) were significantly higher in birds fed with Zn-supplemented diets (p<.05). In treatments supplemented with ZnO-NPs and Zn-methionine, the SOD activity in the liver, pancreas, and plasma was greater as compared with the other treatments (p<.05). The MDA content in eggs was significantly reduced in groups supplemented with Zn (p<.01). Moreover, dietary Zn supplementation significantly affected serum total protein, albumin, glucose, alkaline phosphatase activity, carbonic anhydrase activity, and Zn level (p<.05). In conclusion, this study demonstrated that dietary supplementation with ZnO-NPs can improve the performance of laying hens. Therefore, ZnO-NPs can enhance zinc absorption in the intestine of aged layers and can be a more suitable source of zinc than regular Zn-oxide in diets.