Three experiments were conducted to determine whether feeding semduramicin at recommended levels would affect the broiler chicken's response to dietary methionine. In Experiment 1, three levels of methionine (0, 0.15, 0.30%) were fed to chicks in battery brooders. In Experiment 2, two levels of protein (18 and 22%) and three levels of methionine (0, 0.15, 0.30%) were fed to chicks in floor pens from 18 to 44 d. In Experiment 3, two methionine supplements were fed during each of the starter (0 and 0.21%, 0 to 18 d) and grower (0 and 0.10%, 18 to 35 d) periods to chicks in floor pens. In all experiments, male commercial broiler chicks were used, and all diets were fed with and without 25 mg/kg diet of semduramicin. The basal diets were based on corn, soybean meal, and poultry oil. In Experiment 1, there was a growth and feed conversion ratio response to methionine supplements, but there was no effect of semduramicin on growth nor any semduramicin by methionine supplement interaction. In Experiment 2, at 44 d, protein and methionine levels both influenced feed conversion ratios, but semduramicin did not. Feeding 22 vs 18% protein increased carcass and breast muscle yields and decreased abdominal fat pad weights. The results of Experiments 2 and 3 were very similar. Overall, the effects of semduramicin on growth and processing parameters were small and not significant, but considerable benefits in performance and carcass parameters could be realized by feeding the higher levels of protein or methionine.