Diabetic cardiomyopathy, a major cardiac complication, contributes to heart remodelling and heart failure. Our previous study discovered that CCAAT/enhancer-binding protein β (C/EBPβ), a transcription factor that belongs to a family of basic leucine zipper transcription factors, interacts with the angiotensin-converting enzyme 2 (ACE2) promoter sequence in other disease models. Here, we aimed to determine the role of C/EBPβ in diabetes and whether ACE2 expression is regulated by C/EBPβ. A type 1 diabetic mouse model was generated by an intraperitoneal injection of streptozotocin. Diabetic mice were injected with a lentivirus expressing either C/EBPβ or sh-C/EBPβ or treated with valsartan after 12 weeks to observe the effects of C/EBPβ. In vitro, cardiac fibroblasts and cardiomyocytes were treated with high glucose (HG) to investigate the anti-fibrosis, anti-apoptosis and regulatory mechanisms of C/EBPβ. C/EBPβ expression was down-regulated in diabetic mice and HG-induced cardiac neonatal cells. C/EBPβ overexpression significantly attenuated collagen deposition and cardiomyocyte apoptosis by up-regulating ACE2 expression. The molecular mechanism involved the binding of C/EBPβ to the ACE2 promoter sequence. Although valsartan, a classic angiotensin receptor blocker, relieved diabetic complications, the up-regulation of ACE2 expression by C/EBPβ overexpression may exert greater beneficial effects on patients with diabetic cardiomyopathy.