Peritoneal dissemination or metastasis is a relatively rare presentation of renal cell carcinoma. We report four cases of advanced renal cell carcinoma with peritoneal metastases treated with nivolumab. Three cases showed an objective response in the metastatic lesions including peritoneal sites. After nivolumab administration, the computed tomography scan showed a transient enlargement of peritoneal lesions in two cases, which could be considered as pseudoprogression. Temporal changes of neutrophil-tolymphocyte ratio, C-reactive protein, and eosinophil ratio during the clinical course reflected the treatment effect of nivolumab in these patients, indicating that these could be potential biomarkers of the response. To our knowledge, this is the first case series showing therapeutic activity of nivolumab against peritoneal metastases in patients with renal cell carcinoma.