This study was undertaken to evaluate the influence of levamisole on the immune enhancement of Nile tilapia (Oreochromis niloticus) against potential bacterial pathogens, Fish with weight of 98±5 g were randomly distributed into seven groups each at a rate of 20 fish per 300-L aquarium and fed on a diet containing 0.0, 250, 500, 750, 1000, 1250 or 1500 mg levamisole/kg diet for eight weeks.