A major breakthrough in cancer immunotherapy was the development of monoclonal antibodies targeting inhibitory immune checkpoint proteins. This approach demonstrated significant antitumor activity and efficacy in different cancer types, including metastatic renal cell carcinoma (mRCC). In the majority of patients, this drug is able to restore the patient's tumour-specific T-cell-mediated response thus improving both overall survival and objective response rate. However, a lack of clinical response occurs in a number of patients, raising questions about how to predict and increase the number of patients who receive long-term clinical benefit from immune checkpoint therapy or not. The aim of this review is to summarize available data about immune biomarkers in patients with mRCC treated with immunotherapy.