Abstract Objectives To investigate the long-term follow-up outcomes of nivolumab monotherapy for previously treated metastatic renal cell carcinoma, using real-world data. Methods A total of 121 patients were treated with nivolumab monotherapy as subsequent therapy after the failure of prior tyrosine kinase inhibitor therapy between January 2013 and December 2021 at four affiliated institutions. To evaluate the outcome after 2 years or more, we selected patients in whom nivolumab therapy was started in December 2019 or earlier because data collection was performed until the end of December 2021. Results Seventy-four patients were evaluated. During the median follow-up period of 25.8 months, 62 (84%) and 40 (54%) patients had disease progression and died, respectively. Nivolumab was administered as second-line therapy in 43 patients (58%). The median progression-free survival and overall survival were 5.52 and 31.1 months, respectively, and objective response rate was 36%. There was no difference in progression-free survival or overall survival based on the treatment line of nivolumab (P = 0.915, P = 0.559). The magnitude of tumor response and development of immune-related adverse events were significantly associated with progression-free survival (P < 0.0001, P < 0.0001, respectively) and overall survival (P < 0.0001, P = 0.0002, respectively). Treatment-related adverse events developed in 38 patients (51%), including 33 (45%) who had immune-related adverse events. Steroid administration was needed in nine patients (12%). Conclusions The present real-world multi-institution study with long-term follow-up data demonstrates that nivolumab monotherapy is effective for previously treated metastatic renal cell carcinoma, prolonging survival, improving tumor response and has a manageable safety profile. The real-world data with long-term follow-up indicated that nivolumab monotherapy is effective for previously treated metastatic renal cell carcinoma, prolonging survival, improving tumor response, and has a manageable safety profile.