This study examined the effects of different concentrations of nano zinc oxide (ZnONPs) on the features of the carcass, weight of the bursa and thymus, kidney and liver functions, thyroid hormones, and humoral immunity in broilers that were reared from 1 to 35 days old. 360 male birds (arbor acres) one days old were comprised into six treatment groups. Each group consisted of six replicates.  Six diets were designed to cover the nutritional needs of chicks, with the exception of zinc, which was given at three levels: 100% (of the strain guide recommended level), 50%, and 25% of traditional or nano zinc oxide was given. The results showed that the inclusion of ZnONPs   significantly enhanced carcass weight in the source major effect when compared to the conventional source. Furthermore, the addition of ZnONPs at different levels resulted in the best carcass weight in the interaction (source x level). The percentages of the dressing, abdominal fat, bursa, thymus, and giblets (liver, gizzard, and heart) in the main source, levels, or interaction between treatments did not differ significantly. Additionally, birds fed diets containing ZnONPs showed enhanced immunity (humoral immunity). No significant differences between the different ZnONPs levels were detected. Thyroid hormone levels, kidney and liver functions did not significantly differ amongst the different treatments. According to the current findings, it could be concluded that adding ZnONPs had the best effects in terms of carcass weight and humoral immunity without having a negative effect on thyroid hormones, liver, or kidney function.