Nephrogenic adenoma is an uncommon benign lesion of the urinary tract induced by chronic irritation of the vesical mucosa, due to infection, trauma, surgery, calculi, foreign bodies and chemical agents. A 68-year-old male was admitted to our linic for a periodical cystoscopic evaluation as part of a follow-up initiated due to a past transitional cell carcinoma. The scheduled cystoscopy revealed, within a bladder diverticulum, an unexpected and completely asymptomatic nephrogenic adenoma that we removed by transurethral resection. We followed up the patient at 24 months, then later we made the diagnosis of nephrogenic adenoma. During this time, the patient experienced three relapses within the same diverticulum, always involving a nephrogenic adenoma we persistently treated by transurethral resections. As the nephrogenic adenoma is considered a benign lesion without any direct evidence of a possible evolution to an overt cancer, we successful attempted a half-yearly cystoscopic follow-up to control the growth of a highly recurrent benign entity, interposing between controls a periodical imaging. This paper represents the second report of a nephrogenic adenoma within a bladder diverticulum, but the first case of a nephrogenic adenoma highly recurrent within the same diverticulum and managed conservatively by regular transurethral resection scheduled over the time.