In this study, we examined cardiac inflammation, fibrosis and left ventricular (LV) function during the development of streptozotocin (STZ)-induced diabetic cardiomyopathy using an animal model of diabetes mellitus (DM). Diabetes was induced in 22 Sprague‑Dawley rats by an intraperitoneal single injection of STZ (70 mg/kg). Non-diabetic animals served as the controls (n=6). LV function was documented using the conductance catheter technique 2 and 6 weeks after the induction of diabetes. Cardiac tissue was analyzed for cardiac immune cell infiltration, oxidative stress and remodeling in rats with STZ-induced diabetes at 2 different time points by immunohistochemistry. Cardiac function was significantly impaired in the diabetic animals. After 2 weeks, the induction of diabetes resulted in impaired cardiac function indexed by a decrease in systolic and diastolic LV function. This impairment of LV performance continued for up to 6 weeks after the STZ injection. This was associated with an increase in cardiac CD3+ and CD8a+ immune cell invasion and fibrosis, indexed by an increase in collagen content (p<0.05). Furthermore, oxidative stress response and matrix remodeling were increased after 2 weeks and this continued for up to 6 weeks after the induction of diabetes. In conclusion, cardiac dysfunction is associated with cardiac inflammation and adverse remodeling in experimental diabetic cardiomyopathy. Our results suggest that the model of STZ-induced diabetic cardiomyopathy is a robust model for investigating cardiac immune response and LV remodeling processes under diabetic conditions.