The aim of this work was to investigate the effect of dietary thyme, Thymus vulgaris and rosemary Rosmarinus officinalis on controlling Aeromonas hydrophila (A.hydrophila) infection in Nile tilapia, Oreochromis niloticus (O. niloticus). Fish were divided into three groups in duplicate and fed on experimental diets (0% control, 1.5% thyme and 0.5% rosemary) for 6 weeks before challenge trial with A. hydrophila. Three sampling point were carried out after 2, 4 and 6 weeks post-feeding. Results revealed that serum lysozyme activity recorded significant increase after 2 weeks in both treated groups compared to controls. Serum nitric oxide recorded significant decrease in thyme supplemented group along the experiment. Nile tilapia fed thyme or rosemary exhibited significant (P < 0.05) increase in total leukocytes count, neutrophils and monocytes throughout the experimental period. Meanwhile, lymphocytes recorded significant increase in both treated groups after 4 and 6 weeks feeding compared to the control. In addition, thyme treated group showed significant increase in superoxide dismutase (SOD) and glutathione reductase (GR) enzymes activities after 4 weeks feeding. The level of Malondialdehyde (MDA) was significantly decreased at 6 weeks feeding compared to the control. The challenged fish fed 1.5 % thyme and 0.5 % rosemary for 4 and 6 weeks, showed high survivability 90 % compared to only 10 % of the control. It could be concluded that dietary supplementation of thyme and rosemary in Nile tilapia diet could increases resistance of fish to A. hydrophila through improvement of immune-hematological parameters.