Microbial resistance in livestock has become a subject of great concern of public and scientific interest. This study was designed to assess the effects of methenamine feeding regime on growth performances of broilers chickens. For this purpose, 120 chicks of Cobb 500 strain, including 60 males and 60 females of 21 days old with an average weight of 639 g and 584 g respectively were used. They were randomly distributed in 60 experimental units of 2 chicks of same sex per cage until 49 days. Methenamine was incorporated in feed (TA), acidified (TEa) and non acidified (TE) water and compared to an antibiotic medicated diet as positive control (T0 + ) and a ration without any supplement as negative control (T0). The main results showed that, regardless of the feeding regime, methenamine significantly (p < 0.05) increased feed inteake, body weight, weight gain and decreased (p < 0.05) feed conversion ratio. Methenamine whatever the feeding regime induced a significant increase in lactic acid bacteria counts compared to coliforms and coccidies counts. Salmonella were absent throughout the trial period. Regardless of sex and feeding regime, hematological parameters were not significantly affected, with the exception of white blood cell and platelet concentration that decreased significantly (p < 0.05) in male broilers. Serum content in ASAT (Aspartate-transferase), ALAT (Alanine-transferase), creatinine, urea and LDLcholesterol decreased significantly (p < 0.05), while HDL-cholesterol increased. Histology of organs was not affected. Feeding methenamine to broiler chickens through drinking water can be used as an alternative to antibiotic