Partial nephrectomy aims to maintain renal function by nephron sparing; however, functional changes in the contralateral kidney remain unknown. We evaluate the functional change in the contralateral kidney using a diethylene triamine penta-acetic acid (DTPA) renal scan and determine factors predicting contralateral kidney function after partial nephrectomy. A total of 699 patients underwent partial nephrectomy, with a DTPA scan before and after surgery to assess the separate function of each kidney. Patients were divided into three groups according to initial contralateral glomerular filtration rate (GFR; group 1: <30 ml/min/1.73 m2, group 2: 30-45 ml/min/1.73 m2, and group 3: greater double equals45 ml/min/1.73 m2). Multiple regression analysis was used to identify the factors associated with increased GFR of the contralateral kidney over a 4 year postoperative period. Patients in group 1 had a higher mean age and hypertension history, worse American Society of Anesthesiologists score, and larger tumor size than in the other two groups. The ipsilateral GFR changes at 4 years after partial nephrectomy were –18.9%, –3.6%, and 3.9% in groups 1, 2, and 3, respectively, while the contralateral GFR changes were 10.8%, 25.7%, and 38.8%. Age (Beta: –0.105, 95% confidence interval [CI]: –0.213; –0.011 p<0.05) and preoperative contralateral GFR (Beta: –0.256, 95% CI: –0.332; –0.050 p<0.01) were significant predictive factors for increased GFR of the contralateral kidney after 4 years. The contralateral kidney compensated for the functional loss of the ipsilateral kidney. The increase of GFR in contralateral kidney is more prominent in younger patients with decreased contralateral renal function.