The present study was carried out to investigate the effects of thyme and rosemary as feed additives on growth performance, cellular immunity, and protection of Oreochromis niloticus against Aeromonas hydrophila. Fish were divided into 3 groups and fed on three experimental diets (basal diet 0%, 1% thyme, and 1% rosemary). Fish received thyme and rosemary treated diets showed a significant increase (P < 0.05) in weight gain rate, specific growth rate, and average body weight at 2 nd and 4th weeks. Feed conversion ratio revealed significant increase at 4th weeks for thyme treated group compared to the control. Intestino-somatic index was significantly increased (P < 0.05) in thyme fed group at 6th weeks while Hepato-somatic index exhibited significant increase (P < 0.05) at 2 nd weeks post feeding for rosemary treated fish. Blood parameters showed that total erythrocytes, packed cell volume, hemoglobin concentration, total leucocytes and differential leukocytic count were significantly increased in thyme treated group at 6 th weeks. Fish fed on rosemary-supplemented diet revealed significant increase in total leukocytic counts at 4th and 6th weeks, while differential leukocytic count had significant increase along the experimental period. Serum lysozyme activity was significantly increased in thyme fed group along the whole period and in rosemary treated group at 2nd and 4th weeks in relation with control. Nitric oxide was significantly lower in thyme fed group than the control group. Antioxidant enzymes Superoxide Dismutase, Catalase and Glutathione Reductase revealed significant increase (P < 0.05) with significant decrease of malondialdehyde in thyme treated group in relation with control. Challenge infection by A. hydrophila showed highly significance protection with survivable rate of 90 % in groups fed with rosemary and thyme for 6 weeks. The results suggested that thyme and rosemary can be recommended as a supplementary for O. niloticus increasing the protection against A. hydrophila.