The study was conducted to assess the effects of Effective Microorganisms (EM) as feed additive in broiler chicken production on growth performance, health and foul smell control in poultry house. The experiment involved two hundred and ten, day old hybro broiler chicks which were randomly allocated to 14 pens each with 15 birds in seven treatments with two replicates. The main treatment (EM) was provided to experimental birds in two levels: 10mlEM2/l and 20mlEM2/l either in drinking water or by spraying in litter material or both in water and litter. After 42 days of the experiment 70 live chickens were selected and 5 birds/pen from each replicate were slaughtered for carcass assessment. There were significant difference between treatments on growth performance and carcass yield. EM treated groups had significant higher body weight gain, cumulative body weight gain and average daily body weight gain compared to no-EM control group. Carcass yield percent were comparatively higher in EM treated birds than control groups. T7 had significantly high carcass yield percent (79.13%) compared to other treatments and control group (73.91%). Internal organs such as gizzard and liver had significantly higher weights for EM treated birds compared with no-EM control birds. The overall mortality rate of birds was 12.8% and the highest mortality rate occurred in the first week (9%) and in the second week (3.3%), due to sudden death syndrome, salmonellosis, and huddling. Significant differences were also observed between treatment effects and treatment combinations on ammonia concentration. Pens with birds receiving 20mlEM/l both in water and litter had significant low ammonia levels compared with control group. It is concluded that EM had growth promoting effects, reduced mortality rates and reduced significantly the ammonia levels in poultry house in higher dose of 20mlsEM2/l concurrently supplemented in water and sprayed in litter.