This investigation was designed to evaluate the feed additive potential and antibacterial effect of some medicinal plants as fenugreek, cinnamon, fennel and anise.  A total of 405 unsexed Gimmizah chicks (4 weeks of age) were randomly assigned to nine treatment groups, three replicates (each contained 15 chicks). All chicks were raised in battery brooder placed in a temperature-controlled room until 16 wks of age.  Chicks in 1, 2, 3 and 4 treatments were fed basal diet supplemented with 1g fenugreek, cinnamon, fennel and anise/kg of diet, respectively. Chicks in treatments 5, 6, 7 and 8 were fed basal diet supplemented with 0.5, 1.0, 1.5 and 2.0 g of equal mixture from the previous medicinal plants / kg diet, respectively.  The last group of treatment was used as a control and fed basal diet without any supplementation (T9). Body weight and body weight gain for birds fed basal diet supplemented with 1 g fenugreek /kg diet (T1) at 16 weeks of age had increased significantly by 24.0 and 26.0 %, respectively, than control group (T9), and they also increased significantly (P<0.05) by 9.03 and 10.0 %, respectively, than the chicks fed 2.0 g/Kg of equal mixture (T8). Supplementation of fenugreek alone (T1) increased significantly feed intake through the experimental period (80.63 g/chick/day) as compared to the other treatments. The best feed conversion was recorded (4.23 g/kg diet) for the chicks fed basal diet supplemented with 2.0g/kg of equal mixture medicinal plants (T8), while the worst was recorded for the chicks in control group (T9). Supplementation of fenugreek alone (T1) and the mixture at 2.0 g /Kg (T8) increased significantly the absolute carcass weight and its percentage (1082.9 g and 70.87% for T1 and 1014.4 g and 72.38% for T8) as compared to the other treatments. However, there were no significant differences among the percentage of cocks gizzard, liver, spleen and testes weight due to the different treatments Total cholesterol and the level of Alanine transaminase in blood plasma decreased significantly with supplementation of medicinal plants which studied alone or in the mixture form compared to control group. The total of aerobic and anaerobic bacterial counts and the counts of total coliform were decreased due to supplementation of the basal diet with medicinal plants as compared to control (T9). The greatest reduction of bacterial count was observed with the chicks fed the basal diet supplemented by medicinal plants in a mixture form. Liver, jejunum and ileum  DNA concentration were significantly greater for both chicks groups fed basal diet supplemented with  fenugreek (T1) or with 2.0 g of mixture/kg diet (T8) than the other treatments. The lowest liver, jejunum and ileum DNA concentration was detected for control group (T9).  Supplementation of medicinal plants studied either individual or in a mixture form to the basal diet increased the economical efficiency (EE). Generally, the best EE was recorded for the chicks fed basal diet supplemented with  medicinal plants in a mixture form at levels 2 g /Kg (T8) and 1.5 g /Kg (T7) (0.375, 0.296, respectively).