Reports of primary large cell neuroendocrine carcinomas of the urinary bladder are few; we identified only 2 cases in the literature. Both of these cases involved male patients with rapid progression of disease culminating in death with widespread metastases. We report a case of primary large cell neuroendocrine carcinoma of the bladder, with an admixed minor element of adenocarcinoma, in an 82-year-old man. This solitary lesion arose in a bladder diverticulum lateral to the left ureteric orifice. Two attempts at transurethral resection were unsuccessful at achieving local control. The patient underwent a partial cystectomy with left-sided pelvic lymphadenectomy following preoperative staging investigations that found no metastatic disease. Pathologically, the tumor invaded into the deep aspect of the muscularis propria, without extension into perivesical fat. The lateral resection margin was microscopically positive for tumor, but no malignancy was found in the pelvic lymph nodes. The adenocarcinoma comprised less than 5% of total tumor volume, and areas of transition between the neuroendocrine and adenocarcinoma components were apparent. The patient developed a local recurrence 8 months postoperatively, which was managed by a combination of transurethral resection and radiation therapy. Currently, the patient has no evidence of local or metastatic disease 2 years after initial diagnosis.