Extranodal NK/T-cell lymphoma (ENKTL) is a subtype of non-Hodgkin's lymphoma that accounts for approximately 3-8% of all malignant lymphomas. So far, ENKTL has no standard treatment guidelines, and the current treatment methods pose adverse effects. The combination of programmed death receptors (PD-1) and programmed death receptors' ligands (PD-L1) downregulates effector T cells; hence, it may be an effective treatment for NK/T-cell lymphoma. Here, we report a patient diagnosed with ENKTL whose health was significantly improved after PD-1 immunotherapy. At the same time, the patient suffered from related renal toxic side effects. Immunotherapy is an emerging treatment method for tumors, and the early diagnosis and identification of its side effects are vital for the diagnosis and treatment of tumors.Laboratory tests, pathological examinations, and the patient's history were performed to estimate the severity and the cause of renal insufficiency. The patient with ENKTL developed transient renal damage during immunotherapy. During the next treatment and examination, renal insufficiency was irrelevant to PD-1 inhibitors and avoided unnecessary drug withdrawal.In the present case report, we discuss a patient who developed a severe transient renal impairment during immunotherapy and review published studies regarding immunotherapy and its renal-related side effects. We also outline how to critically distinguish whether a patient's kidney injury is anti-PD-1 treatment. We also provide insights to oncologists to develop an effective follow-up treatment plan for early detection and management of any anti-PD-1 treatment side effects.