Alterations in the cardiac structure and function are the hallmarks of diabetic cardiomyopathy (DCM), separate coronary heart disease in diabetic patients. In a streptozotocin-induced diabetic rat model, the current research aimed to investigate the preventive effects of rosemary extract and hesperidin on DCM. Fifty male Rats were divided into five main groups. Group Ι: rats received no drugs. Group Π: STZ (50 mg/kg b.wt.) was given intraperitoneally (i.p.) to rats just once. Group III: Rats treated with insulin at a dose of (2 U/rat/day). Group IV: rats treated with Rosemary extract at a dose of (200 mg/kg b.wt. /day). Group V: rats treated with Hesperidin at a dose of (100 mg/kg b.wt./day). The results showed a marked increase in serum total cholesterol and triacylglycerol concentrations and downregulation in Peroxisome proliferator-activated receptor-γ (PPAR-γ) and Sarcoplasmic reticulum Ca2+-ATPase (SERCA) genes expressions with upregulation in Collagen type IV (COL4) in cardiac tissue of DCM-induced group. Treatment with insulin, rosemary extract, or hesperidin to STZ-induced DCM in rats exhibited a substantial reduction in the levels of triacylglycerol and total cholesterol with an enormous downregulation of COL4 gene expression level in cardiac tissue. However, PPAR-γ and SERCA genes exhibited an enormous upregulation. In conclusion, the results indicated that rosemary extract and hesperidin have a beneficial effect in preventing lipid metabolic disorders and diabetes complications and modify several genes such as PPAR-γ, SERCA, and COL4 participating in cellular pathways which altered in DCM.