Renal involvement in large B-cell lymphoma represents an exceptional manifestation of non-Hodgkin lymphomas. Acute kidney injury (AKI) by lymphomatous infiltration is extremely rare and so far only 19 cases have been reported in the literature. We report a 67-year-old woman who presented with AKI and was found to have large B-cell lymphoma infiltrating her kidneys. The patient was treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) with rituximab, and a dramatic improvement of renal function was noticed after two weeks of treatment. Her renal function completely recovered after four weeks of treatment. In conclusion, lymphomatous infiltration of kidneys can directly lead to AKI. Rapid diagnosis and treatment is essential to preserve the renal function. Renal biopsy is the gold standard for the early diagnosis of non-Hodgkin lymphoma as a cause of AKI.