An experiment was conducted to determine the effects of a commercial acidifier feed additive product containing formaldehyde on performance, Salmonella typhimurium prevalence and immune status of broiler chickens. Three hundreds, day-old chicks (Hubbard breed) were randomly distributed into three treatment groups (4 replicates each) using 25 chicks per replicate on floor pens. Control (C) birds were offered non-supplemented basal diets. Treatment groups 1 and 2 (T1 and T2) were fed diets containing product at 250 and 500 g tG 1 feed, respectively. Feed and water were offered ad-libitum for 35 days experimental period. Feed consumption and body weight were recorded weekly to calculate body weight gain and feed conversion. Blood samples were collected by time intervals to evaluate the immune status of the birds against some vaccines. At day 21 of age,20 birds were chosen randomly from each group (5 from each replicate) and were challenged orally with 1 mL containing 10 6 colony forming unit (CFU mLG 1) Salmonella typhimurium and were kept under observation for two weeks. At the end of the experimental period, 20 birds were chosen randomly from each group (5 from each replicate) to compare carcass yield. The results revealed that body weight gain was significantly (p<0.05) improved in chicks fed on diets containing product compared with the control one. The best feed conversions were recorded in T2. The results of the Salmonella typhimurium challenge experiment showed that both doses of the products significantly (p#0.05) reduced the signs, mortalities, gross lesions, shedding rate and re-isolation of Salmonella typhimurium. Dressing percentage and liver weight were non-significantly different between groups. Supplementation of the broiler diets significantly enhanced the immune responses measured against the vaccines used. It can be concluded that, using acidifiers and formaldehyde as feed additives for feed sanitation reflected positively on the zootechnical performance of broiler chickens, reduced the incidence of salmonellosis and enhanced the immune status of broiler chickens.