The aim of the present study was to investigate the effect of dietary supplementation with lemon balm (Melissa Officinalis) and Thyme on growth performance, body composition, blood parameters and antioxidant of Nile tilapia fingerlings. One hundred and eighty Nile tilapia (Oreochromios Niloticus) fingerlings were randomly divided into four groups of 45 fish each. Each treatment group was further sub-divided into three replicates of 15 fish per replicate. The groups were fed nearly isocaloric and isonitrogenus diet for 8 weeks as the following:  group 1, fed control diet, group 2 fed control diet + lemon balm (2%), group 3 fed control diet + thyme (1%) and group 4 fed control diet + mixture of lemon balm (1%) and thyme (0.5%).
The obtained results confirmed significant (P<0.05) improvement in fish final weight, weight gain, specific growth rates, feed utilization (feed intake and feed conversion) and protein efficiency ratio by dietary supplementation with Lemon balm and Thyme especially as mixture. These feed additives, also, significantly improved fish serum protein, globulin, cholesterol, TG, super oxide dismutase, glutathione peroxidase and liver enzymes as well as improved fish health. So, it could recommend the addition of 1% Lemon balm + 0.5% Thyme to Nile tilapia fish diet.