BACKGROUND Copper (Cu) is a key trace mineral involved in a variety of physiological processes, and is commonly used in poultry production. However, regardless of the inclusion level the majority of Cu is excreted with poultry faeces. We hypothesise that in ovo administration will allow for better utilisation of Cu during embryo development than when supplied post‐natally with feed to growing chickens. Thus, the objective of this study was to evaluate effects of in ovo administration of NanoCu and copper sulfate (CuSO4) on broiler chicken performance. RESULTS The study showed the positive influences of Cu nanoparticles and CuSO4 on broiler chickens performance. Body weight, at the end of the rearing period (day 42) was significantly higher in NanoCu (2206 g) and CuSO4 (2402 g) groups compared to the control group (2000 g). Both treatment groups had significantly lower feed conversion rate and mortality, and higher percentage of breast and leg muscles in the carcass versus control. CONCLUSION The in ovo application of Cu colloids may ensure an efficient penetration of Cu into the embryonic tissue with long lasting effects on postnatal growth. The method may provide a successful alternative to using Cu as a feed additive. © 2015 Society of Chemical Industry