Low-grade B-cell lymphoma of mucosa-associated lymphoid tissue involving the kidney is rare. We report a series of 3 cases. The first case occurred in an 83-year-old woman who presented with back pain. The second case was a 53-year-old man with a history of sarcoidosis who was found, in the course of evaluation of sarcoidosis, to have a right renal mass. The third case occurred in a 72-year-old man who had a history of periorbital mucosa-associated lymphoid tissue lymphoma and had been treated with surgery and radiation 1 year prior to this presentation. Histologically, all 3 patients showed infiltrate of uniform small-to-medium-sized lymphocytes with irregular nuclear contours and abundant cytoplasm resembling centrocytes or monocytoid lymphoid cells. The first patient received chemotherapy without complications. The second patient underwent a partial nephrectomy and was asymptomatic at the subsequent follow-up. The third patient developed a pulmonary embolism following nephrectomy, and further follow-up is not available.