Gallic acid (GA) is a natural antioxidant, which scavenges free radicals and protects against oxidative damage. This study was done to examine the effects of gallic acid in myocardial dysfunctions associated with diabetes. Diabetes mellitus type 1 (DMT1) was induced by a single intraperitoneal dose of streptozotocin (STZ, 45 mg/kg). As a result of induction of diabetes, the level of serum glucose, glycated hemoglobin (HbA-1c), homastatic-insulin resistance (HOMA-IR), troponin-T, lipid profiles, as well as the activity of lactate dehydrogenase (LDH) and creatine kinase-muscle bone (CK-MB) were increased. On the other hand, insulin and high-density lipoprotein (HDL) levels were decreased. In addition, the diabetic rats exhibited marked trend for increased malondialdehyde (MDA), hydrogen peroxide (H₂O₂), interlukin-1β (IL-1β), interlukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels, accompanied with decreased reduced glutathione (GSH) content, superoxide dismutase (SOD) and catalase (CAT) activities in the heart tissues. Furthermore, an increase in P53, Bax and caspase-9 in the heart tissues of diabetic rats was recorded, as well as a decline in Bcl2 level. On the other hand, diabetic rats which treated with GA orally at a dose of 25 mg/kg daily for 8 weeks, showed amelioration and improvement in the most tested parameters. The current results suggest that GA owns strong therapeutic potential in treating and regulating diabetes and attenuating its associated complications in the heart.