Background <p>The cardiovascular-kidney-metabolic (CKM) syndrome, a concept introduced by the American Heart Association in 2023, emphasizes preventing cardiovascular disease (CVD). The cardiometabolic index (CMI) serves as a comprehensive measure to predict CVD risk and assess cardiovascular metabolic health. This study aims to examine the association between CMI and CVD risk in individuals with CKM syndrome.</p> Methods <p>Data from 5,530 participants aged 45 and older were analyzed using the China Health and Retirement Longitudinal Study (CHARLS) database. CMI was calculated based on triglycerides to high-density lipoprotein cholesterol and waist-to-height ratios. All participants were followed up over a period of 9 years, with the endpoint event being the occurrence of CVD. Cox regression models were used to analyze the association between CMI and CVD risk. Kaplan-Meier survival analysis was employed to demonstrate the differences in CVD risk among different CMI groups. Subgroup analyses were conducted to explore the applicability of CMI in various subpopulations.</p> Results <p>The CMI of participants who experienced CVD was significantly higher than that of participants who did not experience CVD (0.53 vs. 0.45, <i>p</i> &lt; 0.001). In the fully adjusted Cox regression model, CMI is identified as an independent risk factor for the development of CVD in patients with CKM [Hazard Ratio (HR): 1.07, 95% Confidence Interval (CI): 1.02–1.04, <i>p</i> = 0.006]. Kaplan-Meier survival curve indicated that the highest quartile of CMI was associated with the greatest risk of CVD (Log-rank test, <i>p</i> &lt; 0.001). Subgroup analyses indicate that CMI has a stronger association in patients with CKM syndrome at stage 3 (HR = 1.33, 95% CI:1.07–1.64, <i>p</i> = 0.010).</p> Conclusion <p>Elevated CMI is a critical predictor of CVD incidence in individuals with CKM syndrome, especially in advanced stages.</p>