A total of six treatments, i.e., negative control group (D1), B. licheniformis 7×107 CFU g−1 diet (D2); 1ml essential fennel oil (EFO) kg-1 diet (D3); 1 ml essential garlic oil (EGO) kg-1 diet (D4); B. licheniformis 7×107 CFU g−1 +1 ml EFO kg-1 diet (D5) and B. licheniformis 7×107 CFU g−1 +1 ml EGO kg-1 diet (D6) were added to the diets of Nile tilapia, Oreochromis niloticus to investigate the effects of the respective treatments on the growth, feeding behaviour, hematological and biochemical indices. Fish (1.88 ± 0.12 g) were distributed at a rate of 20 fish per 100-L aquarium and three aquaria have been assigned for each treatment. At the end of the experiment (84-day), results indicated that the highest survival, weight gain and specific growth rate were recorded by fish fed D5 and D6 being statistically different (P<0.05) from other treatment groups. Whereas, the best feed conversion ratio and protein efficiency ratio were observed in D3, D4, D5 and D6 compared with other treatment groups. Fish feed D6 were higher in mouth wrestling and chasing behavior. Fish fed D5 and D6 significantly higher (P<0.05) hematocrit and hemoglobin values also, was effectively enhanced aspartate aminotransferase, alanine aminotransferase, total protein and globulin in comparison to the other treatments. No significant differences were found in the chemical composition of whole body of fish fed different tested diets.