Mullerianosis of the urinary bladder is a rare entity characterized by the presence of an admixture of at least two types of mullerian tissue in the muscularis propria of the bladder. We report a case of mullerianosis of the urinary bladder in a 28-year-old nulliparous woman with no history of pelvic surgery or endometriosis, and the diagnosis of mullerianosis was suggested initially in urine cytopathology report. In this study, previously reported cases of mullerianosis of urinary bladder are reviewed, and differential diagnosis of endometrial-like cells in the urine has been discussed. Fewer than 20 cases of mullerianosis of the urinary bladder have been reported in the literature, and only one of these cases had cytological description in a urine specimen. Most of patients were of reproductive age ranging from 28 to 53 years and had no previous history of pelvic surgery or Cesarean section. The clinical presentations frequently were abdominal/pelvic pain and dysuria/hematuria, which may or may not be associated with menstruation. Radiologic study revealed polypoid, mass-like lesion ranging from 1 to 4.5 cm in size, predominantly involving the dome or posterior wall of the bladder. Histological sections showed two or more of the three related benign mullerian glandular epithelial proliferations—endometriosis, endosalpingiosis, and endocervicosis. Most of the patients have good prognosis with medical management. Diagn. Cytopathol. 2012. © 2011 Wiley Periodicals, Inc.