Background: Nivolumab is a standard treatment for previously treated advanced renal-cell carcinoma (RCC). However, nivolumab is effective in only a limited number of patients; therefore, we evaluated the prognostic value of several biomarkers, including inflammation-based prognostic scores and changes in these scores following nivolumab treatment in Japanese patients with metastatic RCC. Methods: We retrospectively reviewed the medical records of 65 patients with previously treated metastatic RCC and who received nivolumab. MSKCC and IMDC risk, inflammation-based prognostic scores, including neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), lymphocyte/monocyte ratio (LMR), and Glasgow prognostic score before and 6 weeks after the treatment were recorded. Categorical variables influencing disease-specific and overall survival were compared using Cox proportional-hazards regression models. Results: Univariate analysis showed that MSKCC risk score (P = 0.0052), lactate dehydrogenase (LDH) (P = 0.0266), LMR (P = 0.0113), and PLR (P = 0.0017) had a significant effect on disease-specific survival. Multivariate analyses showed that PLR and LDH were found to be independent prognostic factors for disease-specific survival (P = 0.0008, RR = 7.95, 95% CI, 2.16–51.64 and P = 0.0123, RR = 3.92, 95% CI, 1.37–10.80, respectively). The combination of PLR and LDH was the most significant prognostic biomarker in metastatic RCC for disease-specific (P< 0.0001) and overall (P< 0.0001) survival. Changes in LMR and PLR in response to nivolumab were significant prognostic factors for disease-specific survival (P < 0.0001 and P = 0.0477, respectively). Conclusions: The combination of PLR and LDH may be a potential biomarker for estimating disease-specific and overall survival in Japanese patients with metastatic RCC treated by nivolumab. If changes of inflammation-based prognostic scores in response to nivolumab treatment might be improved, nivolumab treatment should be continued.