Eosinophilic cystitis is a rare inflammatory disorder of the bladder, characterized by eosinophilic infiltration of the bladder wall, fibrosis of the mucosa, and muscle necrosis. Ultrasonography, when performed, shows a pseudotumoral mass that can be mistaken for malignancy. We report a case of a woman referred to our department in which an ultrasound showed a bladder mass and the biopsy demonstrated the presence of eosinophilic cystitis. The patient was treated with medical treatment and the outcome was favorable with the disappearance of symptoms and no recurrence at controls. We carry a literature review of cystitis eosinophilic, the ultrasound appearance, and therapeutic modalities.