Background: Radical nephrectomy (RN) is a mainstay of management of localized renal cancer >4 cm. RN is associated with renal functional decline, however impact of age on functional decline is unclear. We investigated impact of age on post RN function, focusing on decline to moderate and severe chronic kidney disease (CKD). Methods: This was a retrospective analysis of patients who underwent RN. Patients were stratified by age (<50, 50-70 and >70 years). Primary outcome was development of denovo CKD-S 3b [estimated glomerular filtration rate (eGFR) <45 mL/min/1.73m2)]. Secondary outcomes included denovo CKD-S 3a (eGFR<60) and denovo CKD-S 4 (eGFR<30). Multivariable logistic regression analysis (MVA) was utilized to identify risk factors for renal functional decline. Linear regression was utilized to identify risk factors for increasing DeGFR. Kaplan-Meier analysis (KMA) was utilized to evaluate functional outcomes for different age groups Results: We analyzed 2436 patients (<50 years, n=513; 50-70 years, n=1344; >70, n=579; median follow-up 31.9 months). On MVA, increasing age was an independent risk factor for CKD-S 3a (HR=3.4-9.4, p<0.001), CKD-S 3b (HR=3.4-7.7, p<0.001), and denovo CKD-S 4 (HR=1.96, p=0.027). On linear-regression analysis, increasing age was significantly correlated with increased delta eGFR (β=-0.212, p<0.001). KMA Comparing <50, 50-70 and >70 demonstrated age-associated declines in 5-year freedom from denovo CKD-S 3a (73.9%; 50-70 53.7%; and >70 37.06%, respectively, p<0.001), denovo CKD-S 3b (92.7%; 71.8%; and 55.5%, p<0.001) and denovo CKD-S 4 (93.7%; 89.8%; and >70 81.2%, p<0.001). Conclusions: Increasing age is a risk factor for progressive and clinically significant renal functional decline after RN. Prioritization for nephron-sparing management may be considered when indicated and oncologically safe and feasible in elderly patients to reduce potential risk of sequelae of functional decline.