The effect of graded levels of grains of selim on the performance, gut microbial population and carcass characteristics of finisher broilers was investigated. Two hundred and four (204) 28 days old broiler chicks (Marshal breed) were randomly allotted to four treatments with each treatment having three replicates of 17 chicks each in a completely randomized design. Finely blended grains of selim was administered through drinking water on treatments 2, 3 and 4 at concentrations of 0.5, 0.7 and 0.9 g per litre while chicks on treatment 1 (control) received 1.0 g per 1.5 litre of antibiotics (Gendox). Chicks were fed ad libitum with isonitrogenous and isocaloric diets containing 20% crude protein and 3000 Kcal/kg metabolisable energy for four weeks. Results showed no significant (P > 0.05) differences among treatments in the final body weight, total weight gain, daily weight gain, total feed intake, daily feed intake and feed:gain ratio. There were differences in the microbial population of the gastro-intestinal tract with colony count decreasing as the concentration of grains of selim increases. Carcass characteristics and organ weights were similar (P > 0.05) except for thigh and spleen weights, and large intestine lengths where differences (P < 0.05) exist. Mortality ranged from 8.47% - 13.47% across treatments. The results indicated that grains of selim have antimicrobial and anthelminthic properties, and promote growth in broiler chickens