The effect of colistin sulfate on reducing Salmonella enteritidis (S.enteritidis) infection in broilers and contamination from broiler carcasses was evaluated. 40000 birds in two separate houses were considered. Colistin sulfate was added in to the feed of the test group as 100g containing 1,200,000IU/ton of feed for the whole period (56 days). To isolate S.enteritidis, samples were taken from different parts of the intestine and cultured in Selenite broth and then on SS agar plates. The suspected colonies were isolated and identified by biochemical and serological tests. It is conducted that the addition of the above mentioned amount of this antibiotic in to the broiler feed could decrease the rate of the infection of flocks and contamination of carcasses with S.enteritidis. The results also indicate that due to addition of colistin sulfate, the live weight gain increases by 14% and the feed conversion rate improves by 8% in this study.