A 43-year-old man presented with left leg pain and an abdominal mass. Sonography and cystoscopy showed a bladder tumour obstructing the left ureteral orifice. The left kidney became nonfunctional. Computerized tomography suggested psoas abscess. Nephrectomy was done. Tumoral cells identified at cytological examination of psoas abscess but they were not found in the pyonephrotic kidney's pus. The patient declined further therapy and died 3 months postoperatively. This is the first case of bladder cancer presenting initially with psoas abscess.