Abstract: The effects of dietary supplementation of five growth promoters: Avilamycin (AM), Protexin (PT), Nutracid Focus (NF), Mannanoligosaccharides (MOS) and Vitacel (VC) were evaluated in broiler chicken by their effects on humoral immunity, growth performance, mortality and feed intake. Diets containing no growth promoter (control), AM (100 mg kg-1), PT (100 mg kg-1), NF (800 mg kg-1), MOS (1000 mg kg-1) and VM 6 (4000 mg kg-1) were fed to broiler chicks (Cobb 500). All diets were formulated to exceed NRC nutrient requirements. Each treatment was assigned to 4 replicate floor pens containing 25 birds that were reared from 1-42 days of age. Body weights and feed consumption were recorded every week and mortality and culled birds were recorded daily. On days 9, 17 and 25 of growth (1 day before and 7, 14 days after first Newcastle B1 vaccination), 20 birds from each treatment were chosen randomly and serum antibodies titers of them were measured against Newcastle vaccine by HI test. Dietary supplementation of growth promoters’ antibiotics significantly decreased (p<0.05) Feed Conversion Ratio (FCR) compared with control fed birds during total rearing period. There were no treatments effects on overall feed consumption, mortality or cull rate. Birds fed MOS and PT had superior (p<0.05) serum antibodies titres at the age of 25 days old.