Previous studies have revealed lymph node density (LND) to be an independent prognostic factor in cancer. However, data from 20 years ago failed to demonstrate the prognostic value of LND in node-positive renal-cell carcinoma (RCC). This study was undertaken to comprehensively investigate the prognostic value of LND in node-positive RCC. Within the Surveillance, Epidemiology and End Results database, we accessed data on patients diagnosed with histologically confirmed node-positive RCC from 2004 to 2014. The cubic spline smoothing technique and Cox regression were used to evaluate the correlation between LND and cancer-specific mortality (CSM). The X-Tile program was used to identify the optimal cut point of LND in node-positive RCC. Robustness of the results in various subgroups was also explored. Univariable and multivariable analyses were performed to determine predictors of CSM. Sensitivity analyses were performed. A total of 1750 node-positive RCCs were identified. We found a nonlinear positive correlation between the likelihood of CSM and LND. X-Tile analysis identified best cut point of LND as 35% with a maximum chi-square of 18.58. Every 10% increase in LND increased CSM by 5% (hazard ratio = 1.05; 95% confidence interval, 1.02-1.07; P < .0001), and LND ≥ 35% was associated with 41% increase in CSM (hazard ratio = 1.41; 95% confidence interval, 1.20-1.65; P < .0001) in fully adjusted Cox regression. Results of sensitivity analyses were consistent with those of the primary analysis. LND is an independent prognostic factor in node-positive RCC and should be incorporated into the cancer staging system. Copyright © 2019 Elsevier Inc. All rights reserved.