Bladder endometriosis is an infrequent cause of a focal bladder mass and may masquerade as a neoplasm on ultrasound imaging. This diagnostic dilemma can be resolved with a multiparametric MRI, which shows characteristic hemorrhagic signals of this entity. We present an unusual case of bladder endometriosis where the patient complained of lower abdominal pain without urinary symptoms and was found to have a bladder mass on ultrasonography. This mass was further investigated by an MRI of the pelvis, which revealed characteristic features of endometriosis; the diagnosis was confirmed on subsequent laparoscopy.