The present study aimed to investigate the potential effects of vitamins (C and E)/melatonin co-administration on the hematologic and hepatic functions and oxidative stress in alloxan-induced diabetic rats. The intraperitoneal injection of alloxan (120 mg/kg b.w. for 2 days) induced a significant increase of blood glucose levels (hyperglycemia) associated with serious hematologic disorders (P < 0.01) evidenced by the decrease in the levels of red blood cell count (RBC) (-18%), hematocrit (Ht) (-18%), hemoglobin content (Hb) (-36%), mean corpuscular hemoglobin (MCH) (-17%), and mean corpuscular hemoglobin concentration (MCHC) (-16%). The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and the plasmatic levels of total cholesterol and triglyceride contents of diabetic rats were, however, noted to undergo significant increases by 42% (P < 0.01), 134% (P < 0.001), 27.5% (P < 0.01), 147% (P < 0.001), and 67% (P < 0.01), respectively, as compared to the control animals. Furthermore, a significant increase in malondialdehyde (MDA) content and a significant decrease in superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were observed in the plasma and hepatic tissues of diabetic rats when compared to the controls. Interestingly, the treatment with vitamins (C, E) in combination with melatonin was noted to reduce the plasma levels of glucose, lower the MDA levels, and restore the hematologic parameters and biochemical and antioxidant levels of diabetic rats back to normal values, alleviating diabetes metabolic disorders in rats.