We hypothesised that copper nanoparticles (NanoCu), because of their high physicochemical reactivity and bioavailability, could be used in much smaller quantities than bulk Cu, consequently reducing excretion of Cu into the environment. The objective of the study was to evaluate the effects of various levels of NanoCu on the development and growth of broiler chickens, in order to establish an optimum level of NanoCu dietary supplementation. Broiler chickens were randomly divided into five groups of 10 birds each. The control group received 7.5 mg Cu/kg feed (standard level) as CuSO₄, while groups fed with complexes of NanoCu and starch received 25%, 50%, 75% and 100% of the standard level of Cu used in the control group. Chicken growth and excretion of Cu, Fe and Zn were measured during the growth period from d 7 to 42. At d 42, the slaughter characteristics, the content of Cu, Fe and Zn in the breast muscle and liver, and the oxidative status were analysed. The results indicate that using NanoCu can reduce the standard level of Cu from CuSO₄ supplementation by 75% without jeopardising animal growth, and at the same time significantly decreasing Cu excretion into the environment.