The current study was carried out to evaluate the effects of dietary supplementation of Coriandrum sativum seed powder (CP) and extract (CE) on some immune functions of Oreochromis niloticus, without or with exposure to the immunotoxicant metal lead (Pb). Fish (n = 300) were divided into ten groups, in triplicate. First group (Cont) was fed on the basal control diet. Second (CP20) and third (CP30) groups were fed on CPsupplemented diets at 20 mg/kg and 30 mg/kg respectively, while fourth (CE20) and fifth (CE30) groups were fed on CE-supplemented diets at 20 mg/kg and 30 mg/kg respectively. Fish of the sixth (Cont-Pb), seventh (CP20-Pb), eighth (CP30-Pb), ninth (CE20-Pb) and tenth (CE30-Pb) groups were exposed to lead (Pb) at 20.2 mg/L and received same diets presented to groups; Cont, CP20, CP30, CE20 and CE30 respectively. The experiment lasted for 45 days. CP and CE dietary supplementation not only significantly enhanced the immune functions, serum lysozyme, nitric oxide, bactericidal activities and relative expression of interleukin-1β (IL-1β) of O. niloticus in a concentration-dependent manner, but also ameliorated the lead-induced immunosuppressive effects, especially in CE30 received groups. Additionally, lead-induced fish mortality and levels of lead residues in fish musculature were significantly reduced in response to feeding on CP- and CE-supplemented diets, especially in CE30. Therefore, it could be concluded that coriander dietary supplementation, especially the extract (CE) at 30 mg/kg diet, could be used to enhance the immune response of O. niloticus and to counteract the immunotoxic effects of lead exposure.