Cardiovascular complications represent a significant health concern for individuals with diabetes mellitus. The relationship between diabetes and cardiovascular diseases is complex and multifaceted, involving a variety of pathophysiological mechanisms. This study aimed to investigate the potential role of the cardiothoracic ratio as a prognostic tool for cardiovascular disorders in patients with diabetes. A retrospective case-control study of 530 adult patients referred to a tertiary care hospital in Saudi Arabia was conducted. Medical records, including chest X-rays, were analyzed to determine the cardiothoracic ratio. Patients diagnosed with diabetes who experienced cardiac disorders had significantly higher cardiothoracic ratios compared to patients with diabetes alone and controls. HbA1c was significantly elevated among patients with diabetes and cardiovascular disorders (mean = 71.5 ± 25.43 mmol/mol) compared to the other patients. There was a significant positive correlation between the duration of diabetes and the cardiothoracic ratio (r = 0.64, P < 0.001). Furthermore, the cardiothoracic ratio above 0.51 was a good discriminator of cardiovascular disorders in patients with diabetes, with an area under the curve of 0.737, sensitivity of 97.1%, and specificity of 87.2%. This study provided comprehensive evidence supporting the association between cardiothoracic ratio and subsequent cardiovascular adverse outcomes in patients with diabetes. We recommend adopting the cardiothoracic ratio as a valuable prognostic tool for risk stratification among people with diabetes.