Objectives: As one of the representative aging societies, we aimed to investigate the role of recently proposed age-adapted chronic kidney disease (CKD) definition and outcomes in Korea.  Methods: This study included 2238 patients from the KoreaN Cohort Study for Outcome in Patients With Chronic Kidney Disease. Patients were categorized into three age groups: <40, 40-64, and ≥65 years old. We defined CKD stages according to the estimated glomerular filtration rate (eGFR) calculated on centrally measured serum creatinine and cystatin C. Primary outcome was composite of renal events including end-stage kidney disease (ESKD), fatal cardiovascular events (FCVE), and mortality. Results: The aged (n = 471, 69.3±2.9 years) patients had more metabolic and cardiovascular comorbidities, poorer socioeconomic status, and worse mental status compared to younger age groups. They had lower eGFR, but a similar proportion of albuminuria. During 5.5±2.2 years of follow-up, 588 (26.6%) ESKD, 182 (8.2%) FCVE, and 138 (6.3%) deaths developed. Unsurprisingly, the aged showed worse ESKD, FCVE, and mortality outcomes. Moreover, higher CKD stage was associated with worse kidney and patient outcomes in Kaplan-Meier estimate. Interestingly, however, the cutoff-off eGFR associated with worse outcomes was different according to the age groups. The aged showed an increased risk for primary outcome from CKD stage 4 (HR 4.03, 95% CI [2.13, 7.62]) and 5 (HR 14.19, 95% CI [6.96, 28.91]) whereas middle-aged patients from stage 2 after adjustment with age, sex, diabetes, previous coronary artery disease, smoking, body mass index, blood pressure, albuminuria, and total cholesterol. In all age subgroups, FCVE was not associated with CKD stages. ESKD risk increased from CKD stage 3b in aged group while middle-aged had increased risk even from stage 2. Conclusions: This study suggested that the age-specific eGFR threshold associated with kidney and patient outcomes should be considered in Korean CKD patients.