Abstract: This study was undertaken to investigate growth performance, blood metabolites and humoral immune response of broiler chicks fed diets supplemented with essential oils of thyme, cinnamon and clove. Two hundred and sixty four days old Ross-308 chicks were weighed and randomly allocated between 24 battery pens. Four iso-nitrogenous and iso-caloric diets including: basal diet (control) and basal diet included 200 mg kg^-1 essential oils of Thyme (THY), Cinnamon (CIN) and Clove (CLO) were formulated to meet bird requirements and fed chicks in starting (1-21 days), growing (22-42 days) and finishing (43-49 days) periods. Each diet was fed to birds in six pens (replicate) with 11 chicks per pen. At 17 and 26 days of age, all 360 chicks were vaccinated against NDV. Blood samples were withdrawn from the wing vein at days 17, 26, 34, 41 and 47 of age. The non-heparinized blood samples (1.5 mL/chicken-one bird per pen) were placed at 37°C for 2 h, centrifuged (3000xg for 15 min.) to separate sera and stored at 20°C until analysis. The sera were applied to HI test to determine Antibody (Ab) to NDV expressed as reciprocal log 2 values for the highest dilution that displayed HI. The data was analyzed based on completely randomized design by GLM procedure of SAS. Body Weight Gain (BWG), Feed Intake (FI) and Feed Conversion Ratio (FCR) were not affected by dietary treatment, except for BWG and FCR during the 22-42 days of age. Chicks fed on THY included diets showed improved FCR and BWG comparing to chicks fed other experimental dietary groups during the growing period. Plasma total cholesterol, triglyceride and HDL were not affected by dietary essential oil inclusion (p>0.05). The highest and lowest levels of RBC and HCT were observed in chicks fed on CLO and CIN-included diets, respectively (p<0.05). Primary antibody response of CON chicks was higher than THY and CIN chicks (p<0.05). Secondary antibody response were not affected by dietary inclusion of essential oil (p>0.05).