Abstract: Objective: A study on the effects of Eupatorium odoratum and Ocimum gratissimum leaf extracts on the growth performance, haematology and cost benefit of broiler chickens were evaluated using 72 day old Anak broiler chickens in the Animal Science Department, Ebonyi State University Abakaliki, Nigeria. Materials and Methods: Four water infusion levels, 0, 25, 25 and 25 mL for control, E. odoratum, O. gratissimum and both leaf extracts per liter of clean drinking water designated as T1 (control), T2, T3 and T4 respectively, were used. The birds were randomly allotted to these dietary infusion levels in a completely randomized design (CRD). Each treatment was replicated 3 times with 6 birds per replicate. Feed intake, weight gain and haematological indices were determined. Economic analysis was also conducted at the end of the 4 weeks experiment. Data was analyzed by one-way ANOVA using Duncan’s new multiple range test. Results: There were no significant (p>0.05) differences in the feed intake as well as weight gain and feed conversion ratio. The growth performance of the broilers fed E. odoratum and O. gratissimum were better than those fed diets without E. odoratum and O. gratissimum. There were significant (p<0.05) differences in the blood components of the broilers under this feeding regime. Packed cell volume (PCV), red blood cells (RBC) and white blood cells (WBC) improved with infusion of leaf extracts. Conclusion: The combination of the leaf extracts gave better result in growth and haematological indices of broiler chickens. These showed that the use of both leaf extracts played more significant role as anti-microbial than without E. odoratum and O. gratissimum leaf extracts in the diets of broiler chickens.