Abstract: Investigation of possible effects of NADH supplementation on hematological and blood biochemical parameters and on oxidant/antioxidant status in some tissues including liver, kidney and heart was aimed in this study. Fourteen Sprague-Dawley type rats of 2 months old were used throughout the study. Seven rats were fed on NADH containing foods for a month and the others were fed on the same food diet except NADH. After a month, blood samples were obtained before animals were sacrificed. Their liver, heart and kidney tissues were removed to be used in the analyses of oxidant/antioxidant parameters. In the NADH group, lowered erythrocyte, leukocyte, platelet, hemoglobin and hematocrit values were observed as compared with control group. Furthermore, increased malondialdehyde and oxidation sensitivity values were measured in the heart tissues from NADH supplemented group. Serum LDH activity was also found to increase in the study group. In conclusion, NADH supplementation causes anemia and leukopenia and leads to increased peroxidation reactions in the heart tissue.