This study was conducted to evaluate the effect of Nano zinc oxide particles (nZnO) supplementation on growth performance, ingestive and standing idle behaviours, serum zinc level and some haematological parameters in cross bred calves. Ten calves at the farm of Faculty of Veterinary Medicine – Aswan University were randomly selected with an average age of 4 months and weight of (80.5±4.0 kg). Calves were divided equally into two groups, control and treatment groups (5) in each group. Each calf in the treatment group was administered daily with zinc oxide Nano particles at the rate of 10 ppm orally for three months. The results revealed that the used rate of nZnO supplementation had no significant effect on the average daily gain of calves throughout the different periods of experiment. Moreover, the average time spent in ingestive behaviour was significantly higher in control group (18.1±0.3 and 16.8±1.4) than treatment group (11±2.1 and 5.7±3) after 2 weeks and 8 weeks respectively. On the other hand, serum zinc level was significantly higher (p < 0.05) in the treatment group (9.2±0.4 µg/dl) than control group (8.0±0.2 µg/dl) after the 12th week. There was no significant effect of supplementation nZnO on the measured haematological parameters.