The experimental trial was carried out to evaluate the impact of a mixture of Bacillus subtilis and Bacillus licheniformis probiotic supplementation via the drinking water (AVI-GROW®) on growth performance, carcass traits, gut microbiome, intestinal histomorphology, blood biochemical indices, and litter quality of broiler chickens. A total of 480 one-day-old Ross 308 broiler chicks (as hatch) were randomly allocated into two groups, each with three replicates (80 chicks/replicate). The control group (T1) and the supplemented group (T2) were fed a basal diet, however, T2 was supplemented with (AVI-GROW®) via the drinking water at the rate of 1mL/L drinking water every 12 hours for 2 days after every vaccination and change of diet. The experiment lasted 31 days. Supplementation of (AVI-GROW®) via the drinking water in T2 significantly (P≤0.05) improved body weight gain and feed conversion ratio (FCR), as well as villus crypt ratio of the small intestine as compared to the control. The dressing percent, breast, thigh and drumstick yields were improved in T2 than in control. Additionally, blood cholesterol, triacylglycerol, ALT, and AST concentrations were reduced, while total protein concentration was significantly (P≤0.05) increased in T2 as compared to control. Moreover, cecal clostridial counts were significantly (P<0.05) lower in T2 as compared to control. Supplementation of (AVI-GROW®) in (T2) reduced nitrogen content in birds' excreta and litter. Conclusively, the supplementation of (AVI-GROW®) via the drinking water could improve growth performance, carcass characteristics, gut microbiome, intestinal histomorphology, blood biochemical indices, and litter quality in broiler chickens.