Because of speculated risk in generating antibiotic resistance in pathogenic microbiota, natural products from plant origin due to their diverse biological activities, have recently gained a great attention in animal nutrition. This study was designed to evaluate graded levels of neem seed oil on growth performance of broiler chickens. A total of 400‐day‐old chicks were randomly allocated to five experimental treatment groups. Experimental rations consisted of supplementing basal diet (R0−) with 1 g antibiotic (R0 + ), 15, 20 and 25 g neem seed oil/kg of feed. Data were recorded on feed intake, weight gain, feed conversion ratio, and serum biochemical parameters. Result revealed that feeding broiler chicks with 25 g of neem oil/kg of feed resulted in a marked (P < 0.05) decreased in feed intake as compared to the other treatments in the starter phase. The average live body weight and the weight gain decreased with increasing level of neem oil in the ration. Supplementation of poultry feed with graded levels of neem oil has no marked (P > 0.05) effect on carcass yield and relative weight of organs except for liver weight which significantly (P < 0.05) increased with the highest dose of neem oil. Serum content in total proteins, total cholesterol, HDL‐cholesterol, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatinine were not significantly (P > 0.05) affected by the graded levels of neem oil. LDL‐cholesterol significantly (P < 0.05) decreased with diets supplemented 20 g of neem oil/kg while triglycerides significantly increased with the highest doses of oil (20 and 25 g/kg) as compared to the negative and positive control rations. In conclusion, feeding broilers with Azadirachta indica seed oil has no beneficial effect on growth performance but may lead to the production of low‐cholesterol chicken meat as demand by health‐conscious consumers.