We report a case of primary mucosa-associated lympoid tissue (MALT) lymphoma of the urinary bladder associated with left renal pelvic carcinoma. A 84-year-old woman showed microscopic hematuria during follow up for hypertention. Left renal pelvic tumor was found and she was referred to our hospital for further evaluation and managemant. She showed pyuria and Escherichia coli was detected by urine culture. Intravenous pyelography and computed tomography revealed the left renal pelvic tumor and solid bladder tumor. Transurethral resection of bladder tumor and left total nephroureterectomy were performed. Histologically, the left renal pelvic tumor was urothelial carcinoma > > adenocarcinoma, G2, pT2 and the bladder tumor was MALT lymphoma. Ga-scintigraphy showed no hot uptake suspicious of metastatic lesion. Then, external beam radiotherapy (36 Gy) was performed to the urinary bladder. She has been alive for 14 months with neither renal pelvic tumor nor MALT lymphoma showing any evidence of disease progression.