To explore the association between rapid eye movement-related obstructive sleep apnea (REM-OSA) and common cardiometabolic diseases (CMDs) in patients with mild OSA. This retrospective study was conducted by reviewing the medical records and polysomnograms (PSGs) of patients at Siriraj Hospital. The PSGs of patients diagnosed with mild OSA who had ≥ 15min of REM sleep were included. REM-OSA was defined if the apnea-hypopnea index (AHI) in REM was ≥ 2 times that of non-REM. Common CMDs included coronary artery disease, stroke, heart failure, diabetes mellitus, and hypertension. The data of 518 patients with a mean age of 48.3years, 198 males, and mean AHI of 9.8 events/h were analyzed in this study. When compared with the control group, the REM-OSA group (308 patients) were predominantly female (72%), overweight (62%), and had more severe oxygen desaturation, p-value < 0.001. CMDs were significantly more common in the REM-OSA group than in the controls [odds ratio (OR) 1.52, 95% confidence interval 1.04-2.21, p-value = 0.029]. Patients with a REM AHI of ≥ 20 events/h were significantly associated with hypertension compared to those with a REM AHI of < 20 events/h, p-value = 0.001. However, these associations were found not to be statisticallysignificant after controlling for age, sex, BMI, and prevalent coexistingCMD (OR = 1.13, 95% CI: 0.72-1.76, p-value = 0.605). Common CMDs, particularly HT, tend to show an association with REM-OSA in patients withmild OSA, but this association did not reach statistically significant levels.