Diabetic cardiomyopathy is characterized by left ventricular hypertrophy, early diastolic dysfunction and/or systolic dysfunction that leads to heart failure in diabetic paients. The endocannabinoid system has a recognized role in the development of various cardiac diseases due to involvement in cardiac dysfunction, inflammation, fibrosis and cell death. In this study, the role of cardiac CB1 receptor signaling was explored in a stertozotocin-induced type 1 diabetic mouse model. The animals with chronically increased blood glucose levels developed characteristic diabetic cardiomyopathy assessed by intraventricular pressure-volume catheter system. At the tissue level, the hearts after 12 weeks of diabetes showed increased myocardial oxidative/nitrative stress, p38/Jun kinase (JNK) and mitogen-activated protein kinases (MAPKs) activation, enhanced inflammation and fibrosis, accumulation of advanced glycation end product (AGE), increased AGE and angiotensin II type 1 (AT1R) receptors, decreased expression of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA2a). Overactivation of the endocannabinoid system due to the diabetes was evident by increased cardiac endocannabinoid anandamide levels and cannabinoid 1 (CB1) receptor expression. Pharmacological inhibition or genetic deletion of the CB1 receptors attenuated the diabetes-induced cellular alterations and improved cardiac dysfunction. Most importantly, pharmacological inhibition of CB1 receptors may preserve its beneficial effects on contractile dysfunction even if administered after the development of established cardiomyopathy. Overactivation of cardiac CB1 receptors by endocannabinoids may play an important role in the pathogenesis of diabetic cardiomyopathy by facilitating various intracellular signaling (MAPK activation, AT1R expression/signaling, AGE accumulation, oxidative/nitrative stress), inflammation, and fibrosis. Conversely, pharmacological inhibition of cardiac CB1 receptor may be beneficial in the treatment of diabetic cardiovascular complications.