The present study was conducted to investigate the effect of using Nigella sativa oil on the health of suckling calves, mortality, growth performance and Eimeria species infection through haematological, biochemical parameters, immune status and faecal examination during conventional and early weaning systems. For these purposes, twenty five newly born Friesian calves were randomly divided into five groups (5 in each); the first group suckled individually on milk for 15 weeks of age until weaning (conventional weaning) without treatment (S15T0), second group suckled for 15 weeks until weaning and received daily 0.06 ml of Nigella sativa oil /Kg body weight for 15 weeks (S15T15), third group suckled for 7 weeks (early weaning) without treatment (S7T0), fourth and fifth groups (S7T15 and S7T7) suckled for 7 weeks and treated with the same dose of Nigella sativa oil for 15 and 7 weeks respectively. The results showed that all calves received Nigella sativa oil did not show symptoms of diarrhea and no animals died during the period of the experiment. On the other hand, the calves which did not receive Nigella sativa oil showed cases of diarrhea and 3 calves died. Also, calves treated with Nigella sativa oil (S15T15, S7T15 and S7T7) clearly showed increase (P<0.05) of haemoglobin concentrations, haematocrit values, white blood cells counts, globulin, IgG and IgM concentrations than non-treated calves (S15T0 and S7T0). On the contrary, serum glucose and total lipids concentrations were decreased (P<0.05) in treated groups, while serum total protein concentrations slightly increased (P>0.05) in treated groups compared to non-treated ones. Insignificant differences (P>0.05) among different groups were observed in concentrations of AST and ALT, which were in the normal range. The mean number of Eimeria sp. oocysts decreased in treated groups compared with non-treated ones. In parallel, slowdown of body weight gain was observed in calves treated with Nigella sativa oil compared to nontreated ones. It could be concluded that the use of Nigella sativa oil for suckling calves was effective in maintaining blood homeostasis, improving general health status and for prevention and treatment of health problems in suckling Friesian calves.