Previous studies have shown that inflammatory process contributes to the pathogenesis of cardiac damage induced by diabetes mellitus. However, the underlying mechanisms and strategies to alleviate inflammatory injury in the diabetic heart are not fully elucidated. In this study, we investigated the potential role and related mechanism of bamboo leaf extract (BLE) on diabetes-induced cardiac fibrosis in rats. Diabetes was induced by streptozocin (STZ) in rats, blood glucose and glycosylated hemoglobin A1c (HbAlc) were measured. Super oxide dismutase (SOD) activity and malondialdehyde (MDA) level in rat heart homogenates were tested using special kits. Cardiac function was evaluated by echocardiography, and myocardial histology was detected by hematoxylin eosin (HE) staining and Masson’s trichrome staining. Furthermore, expression of transforming growth factor-β1 (TGF-β1), interleukin 6 (IL-6) and Cleaved-cysteinyl aspartate-specific proteinase-3 (Cleaved-caspase-3), and the activity of nuclear factor κB (NF-κB) were examined by western blot analysis. From the data, we found that the BLE treatment inhibits oxidative stress and improved cardiac function in STZ-induced diabetic rats. BLE treatment significantly ameliorated diabetes-induced myocardial morphological changes and cardiac inflammation. Moreover, the protein levels of TGF-β1, IL-6,Cleaved-caspase-3 and the nuclear transcription of NF-κB in the hearts were markedly reduced in diabetic rats result from BLE treatment. In conclusion, this study suggested that BLE ameliorates cardiac fibrosis in streptozotocin-induced diabetic rats, and this protective effect possibly through inhibiting inflammation, oxidative stress and apoptosis. BLE might serve as a potential therapeutic target for the treatment of the cardiac fibrosis in diabetic patients.