This experiment was conducted to evaluate the use of ethanol-extracted from the medicinal plant, eugenia Caryophllate as immunity promoter for Nile tilapia, Oreochromis niloticus (L.) fingerlings. Fish (Average 12.27 g) were randomly distributed into four treatments; three replicates each at a rate of 20 fish per 100– L aquarium. Fish were fed one of the tested diets containing similar crude protein (30 %) and gross energy (4.40 kcal / g), in addition to 0.0, 0.5 %, 1.0%, or 1.5 % eugenia caryophllate extract. fish of each treatment were challenged by pathogenic Aeromonas Hydrophila, which was given by intraperitoneal (I/P) injection and they were kept under observation for 10 days to follow up any abnormal clinical signs and the daily mortality rate. meanwhile total protein and albumin, increased significantly (P<0.5) to the highest values at 0.5 % eugenia caryophllate extract, as compared to the control.  WBCs count and Hb values increased with non- significant differences with increase in eugenia caryophllate extract level in fsh diet (P>0.05). This present study, showed that 0.5 % eugenia caryophllate extractin Nile tilapia diets, increased the fish resistance toAeromonas Hydrophila, indicating the effective role of eugenia caryophllate extract in disease prevention in tilapia culture. The reduction in feed cost compared with control diet showed 12.52 % to produce one kg fish gain of treatment containing 0.5 % extracted Eugenia caryophllate levels.