BACKGROUND: Cardiovascular autonomic neuropathy (CAN) is a frequently underdiagnosed complication of diabetes mellitus that contributes to increased mortality and morbidity rates. This multicenter study investigated the epidemiology and clinical characteristics of CAN in patients with long-term diabetes. METHODS: Retrospective data were collected from 884 individuals with diabetes who were assessed for CAN across eight hospitals in Korea. CAN was diagnosed using electrocardiography and cardiovascular autonomic function tests, including the heart rate-corrected QT interval and Ewing's method. This study evaluated the clinical characteristics, cardiovascular autonomic nerve function test results, and risk factors associated with CAN. RESULTS: Among the 884 patients, 778 (88%) were diagnosed with CAN (DCAN), while 106 (12%) were not (non-DCAN). Individuals with DCAN were older, had a longer duration of diabetes, and had higher creatinine levels. The DCAN group showed decreased time and frequency parameters of heart rate variability (HRV). A multiple logistic regression analysis revealed that a longer diabetes duration, older age, and higher creatinine level were significant risk factors for CAN. CONCLUSION: CAN was associated with advanced age, a longer duration of diabetes, higher creatinine levels, and lower time and frequency HRV parameters.