Introduction: Eosinophilic cystitis (EC) is a rare and poorly understood inflammatory condition, characterized by eosinophilic infiltration of all layers of the bladder wall, which mimics bladder tumors. ECmaypresent with symptomssuch as increased urination frequency, dysuria, gross/microscopic hematuria, suprapubic pain and urinary retention. Case Presentation: We present a 17-year-old male patient, who was continent night and day in his childhood, and was admitted to our clinic for complaints of hematuria and nocturnal enuresis for the past six months. His history and physical examination were unremarkable, and routine hematological and biochemical tests were normal. Cystoscopy revealed a 4×3 cm erythematous, polypoidal, solid lesion on the bladder dome. Histopathological examination of the lesion revealed transitional epithelium with stromaledema, wherediffuse, dense infiltration of lamina propriabyeosinophilsandlymphocyteswasalso seen. According to these findings, a histopathological diagnosis of EC was made, and the patient was treated with corticosteroids, antimicrobial agents and antihistamines. His symptoms dramatically improved and nocturnal enuresis also recovered after treatment. Conclusions: Although it is a rare entity, EC should be kept in mind in the differential diagnosis of patients presenting with dysuria, hematuria and any kind of acquired voiding dysfunction, including frequency, pollakiuria and incontinence.