Abstract: Background and Objective: Generous use of antibiotics in the broiler diets is a common practice in the broiler industry for promoting growth and enhance the immune responsiveness. Subsequently, resulted in occurrence of resistance amongst pathogens and potential for residuals in broiler chicken body tissue. The current study was carried out to evaluate the impact of various levels of black cumin seeds (BCS) dietary supplementation on growth performance, mortality and immune response of broiler chickens. Materials and Methods: Two-hundred fifty-five, one-day old Cobb 500 broiler chicks were randomly assigned into three treatment batteries with five replicates of 17 chicks each. Three levels of black cumin seeds (0, 1 and 3%) were fed in the diets of the test broilers, in which the group with 0% served as a control. Results: Diets supplemented with black cumin seeds significantly (p<0.05) improved the growth performance parameters such as body weight, body weight gain, feed consumption, feed efficiency and mortality percent as compared to the control group. In addition, diets supplemented with black cumin significantly (p<0.05) increased the bursa and thymus weights and improved antibody production, as well as the immune-responsiveness of birds. Conclusion: Dietary supplement of black cumin seeds at the level of 1 and 3% may improve production performance and potential for improving immune-responsiveness of broiler chicken.