This study was conducted to evaluate the effect of black seed and marjoram leaves powder on growth performance, feed utilization, and body composition of Nile tilapia, Oreochromis niloticus. All diets are iso-nitrogenous  (30% crud protein).and iso-caloric (4.72 kcal/g diet). Thirty  glass aquaria were used, each one was stocked with 10 fish (8.2 g) and three aquaria were designated for each treatment. The  ten treatments  were: Treatment 1 was control without additives, treatments 2, 3 and 4 contained 1.0%, 2.0% and 3.0% black seeds (BS), respectively, treatments 5, 6 and 7 contained 1.0%, 2.0% and 3.0% marjoram leaves (ML), respectively and treatments 8, 9, and 10 contained BS and ML  (1 : 1 w/w) at a rate of 1.0, 2.0%, and 3.0%, respectively. Fish were fed on one of the experimental diets at feeding level of 3% of body weight daily for 12 weeks. The feed was offered twice daily, five days a week. Fish growth (indicated as final weight, weight gain, daily gain, relative grouth rate ( RGR),and specific growth rate ( SGR)) was  increased gradually and the maximum growth was obtained when fish fed T4. The lowest growth was obtained at the control group. The  highest feed intake and the lowest feed conversion ratio ( FCR) were obtained when fish fed 30 g BS/kg diet (T4). Apparent protein utilization (APU ), and energy utilization ( EU ) were enhanced significantly when fish fed BS and ML (each alone or together), while the lowest values were obtained at the control group. Dry matter content in fish body was significantly incrased by BS and/or ML. Crude protein increased significantly also in all treatments compared with the control. Total lipids contents refleacted significant increases in all treatments compared with the control.Yet, ash content decreased significantly with each black seed and/or marjoram leaves level.