Heart failure (HF) is one of diabetic complications. This work was designed to investigate the possible modulatory effect of curcumin against streptozotocin-induced diabetes and consequently HF in rats. Rats were divided into control, vehicle-treated, curcumin-treated, diabetic-untreated, diabetic curcumin–treated, and diabetic glibenclamide–treated groups. Animal treatment was started 5 days after induction of diabetes and extended for 6 weeks. Diabetic rats showed significant increase in serum glucose, triglycerides, total cholesterol, low-density lipoprotein-cholesterol, very low density lipoprotein-cholesterol, nitric oxide, lactate dehydrogenase, cardiac malondialdehyde, plasma levels of interleukin-6, and tumor necrosis factor-alpha, and also showed marked decrease in serum high-density lipoprotein-cholesterol, cardiac reduced glutathione, and cardiac antioxidant enzymes (catalase, superoxide dismutase, and glutathione-S-transferase). However, curcumin or glibenclamide treatment significantly mitigated such changes. In conclusion, curcumin has a beneficial therapeutic effect in diabetes-induced HF, an effect that might be attributable to its antioxidant and suppressive activity on cytokines.