The objective of this experiment was to investigate the effects of dietary supplementation of probiotics, Lactobacillus acidophilus and Bifidobacterium bifidum, on histo-morphologic measurements of the small intestine and on the gut health status of broiler chickens. A total of 240 day-old broiler chicks were randomly assigned to one of six dietary treatments for six weeks. The dietary treatments were basal diet (T 1); basal diet+ bacitracin methyl di-salicylate (BMD) at 20 mg/kg diet (T 2); basal diet+ L. acidophilus (10 6 and 10 7 cfu/gm diet)(T 3 and T 4); and basal diet+ B. bifidum (10 6 and 10 7 cfu/gm diet)(T 5 and T 6), respectively. The villus height (VH), width (VW), crypt depth (CD) and the ratio between villus height and crypt depth (VH: CD) were significantly increased at 21 days and 42 days in L. acidophilus-supplemented groups (T 3 or T 4). No significant differences were observed in protein, albumin and serum mineral (Ca and P) concentrations and alkaline phosphatase (ALP) activity in any of the dietary probiotic treatment groups. Aspartate aminotransferase (AST) and creatinine concentrations were increased, whereas alanine aminotransferase (ALT), uric acid and total cholesterol levels were significantly decreased in probiotic-supplemented groups. Coliforms and total anaerobes counts were significantly reduced at 21 and 42 days at the ileum and caecal in T 4, whereas the lactic acid bacteria (LAB) Lactobacilli count was significantly increased in all the probiotic-supplemented groups. The results of the present study indicate that L. acidophilus at 10 6 cfu/g feed inclusion in basal diet may improve blood biochemical parameters and histo-morphometry in the intestine and gut health in broiler chickens, resulting in a valid feed additive to replace antibiotic growth promoters.