Abstract: A study with four hundred, 1 day old male (Ross 308) broilers that were randomly assigned to 4 treatments with 5 replicate, 20 birds per each was conducted to determine the effect of diet supplementation with Lactobacillus cultures on some blood parameters, plasma enzymes activities and mortality of broiler chicken. For this purpose, the experiment carried out by feeding 4 levels of the probiotic (0, 0.05, 0.10 and 0.15%) to broiler chicks from days 1-42 of age. Hematological, biochemical tests were measured at days 21 and 42; Hemoglobin (HGB), Hematocrit (HCT), release of Alanine Transaminase (ALT), Aspartate Transaminase (AST), Lactate Dehydrogenase (LDH), White Blood Cell (WBC), heterophils, lymphocytes, cholesterol and triglycerides. The results of the recent experiment showed that feeding diet with Lactobacillus cultures (0.15%) to chickens significantly (p<0.05) decreased, ALT and AST activity, cholesterol and triglycerides. Moreover, Lactobacillus cultures (0.15%) significantly (p<0.05) increased HCT, HGB and WBC day 42 of age. Moreover, Lactobacillus cultures (0.15%) significantly reduced chicken mortality compared to the other groups. There are no significant effects of Lactobacillus cultures on other blood parameters.