BMI, metabolic health status, and their interactions should be considered for estimating mortality risk; however, the data are controversial and unknown in Asians. We aimed to investigate this issue in Korean population. Total 323175 adults were followed-up for 96 (60-120) (median [5-95%]) months in a nationwide population-based cohort study. Participants were classified as "obese" (O) or "non-obese" (NO) using a BMI cut-off of 25 kg/m(2). People who developed ≥1 metabolic disease component (hypertension, diabetes, dyslipidaemia) in the index year were considered "metabolically unhealthy" (MU), while those with none were considered "metabolically healthy" (MH). The MUNO group had a significantly higher risk of all-cause (hazard ratio, 1.28 [95% CI, 1.21-1.35]) and cardiovascular (1.88 [1.63-2.16]) mortality, whereas the MHO group had a lower mortality risk (all-cause: 0.81 [0.74-0.88]), cardiovascular: 0.73 [0.57-0.95]), compared to the MHNO group. A similar pattern was noted for cancer and other-cause mortality. Metabolically unhealthy status was associated with higher risk of all-cause and cardiovascular mortality regardless of BMI levels, and there was a dose-response relationship between the number of incident metabolic diseases and mortality risk. In conclusion, poor metabolic health status contributed more to mortality than high BMI did, in Korean adults.