An experiment was conducted to evaluate the effect of supplementation of broiler diets with benzoic acid on intestinal micro flora and haematological indices. One hundred and twenty (120) birds were used which was divided into five treatments of three replicates with eight birds per replicate arranged in a completely randomized design (CRD). The levels of benzoic acid inclusion were 0, 0.6, 1.2, 1.8 and 2.4%. Commercial feed containing benzoic acid was given every morning and evening. Water was given ad libitum. The experiment lasted for 49 days. Data on microbial load, pH and haematological indices were collected at the end of the experiment. Blood samples were collected through the Jugular vein. Chyme samples were collected from the intestine lumen and analyzed. The result showed that there was no significant difference (P<0.05) between the pack cell volume (PCV), haemoglobin (Hb), white blood cell (WBC), red blood cell (RBC), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration MCHC). The pH of the crop and colorectal were not significantly different, while the pH of the gizzard, duodenum, ileum and caecum were significantly different (P<0.05) from each other across the levels of treatment. The pH value of gizzard was the least on T₄, while the highest value of pH was recorded in colorectal T₄. The microbial load decreased significantly (P<0.05) with increased inclusion of benzoic acid in the feed. The least microbial load was recorded in duodenum and ileum at T₄, while the gizzard and caecal microbial load were 5.01 x 10⁵ in T₄. This study showed that supplementing broiler diets with benzoic acid as antibiotic substitute reduced the intestinal microbial load with a corresponding increase in their pH without a significant effect of the haematological indices.