Müllerianosis of the urinary bladder is an extremely rare, benign condition defined by the presence of at least two of the three müllerian-derived components (endosalpinx, endometrium, and endocervix) in the lamina propria and muscularis propria of the urinary bladder. It frequently mimics neoplastic condition, either malignant or benign. Here, we present a case of cystic müllerianosis of urinary bladder, which was clinically thought to be a urinary bladder neoplasm.