The aim of the present study was to evaluate the effect of addition of Enterococcus faecium M74 in drinking water on performance and carcass characteristics of broiler chickens. Totally 120 chickens (60 of hybrid Hybro, 60 of Ross 308) were divided to two groups. Experimental chickens of Hybro (n= 30) and Ross 308 (n= 30) received a probiotic preparation in drinking water from day 1 to day 42 with concentration of 2x10 9 CFU of Enterococcus faecium M 74 in 1 g of nutrient medium with dextrose. The control group of Hybro (n= 30) and Ross 308 (n= 30) received water in same total amount as experimental group without any additives. The feeding period lasted 42 days. In case of Hybro, we showed higher effect of Enterococcus faecium M74 supplementation on slaughter weight (1807.51 vs. 1929.08 g; P< 0.05) in comparison with Ross 308 (2126.63 vs. 2199.31 g; p> 0.05). Differences in percentage of valuable parts (thigh and breast) and carcass yield of Hybro and Ross 308 were not statistically significant (p> 0.05) by addition of probiotic On the end of fattening, Ross 308 broiler chickens fed diet with probiotic strain Enterococcus faecium had significantly less (p< 0.05) abdominal fat than those fed without the probiotic. In Hybro broiler chickens we recorded not significant difference between groups (p> 0.05).