Efficacy of bacteriocin-divercin AS7 supplementation of broiler diets was evaluated. In two experiments one-day-old Ross 308 males were allocated randomly to six and eight dietary treatments, respectively, with 10 replicates (10 birds per replicate). In both experiments the birds were fed on diet non supplemented (negative control, NC) and supplemented with salinomycin (positive control, C). In Experiment 1, the effects of supplementation of the NC diet with 100, 200 or 800 units of liquid divercin, and in Experiment 2 with 100, 200 or 300 units of lyophilized divercin added in encapsulated or non-encapsulated form, were studied during starter and grower period. The response of birds in terms of feed intake, body weight gain (BWG) and feed efficiency (FE) depended on the growth period. In Experiment 1, supplementation of salinomycin or liquid divercin did not affect feed intake and BWG while FE was significantly improved by salinomycin. In Experiment 2, BWG was significantly improved by supplementation with salinomycin, all doses of non-encapsulated and the lowest dose of encapsulated divercin. In Experiment 1, the metabolizable energy content and fat digestibility tended to be greater in birds fed on diets supplemented with salinomycin and divercin than on NC diet, while in Experiment 2 were significantly greater on diet supplemented with salinomycin than on all other diets. It is suggested that divercin AS7 may improve performance of chickens but its efficacy depends on physical form.