BACKGROUND: In the United States, vesico-vaginal fistula formation is most commonly associated with prior gynecologic surgery, and only rarely with severe pressure necrosis. CASE: A 16-year-old girl presented with continuous urinary leakage and malodorous discharge. Examination revealed an incarcerated plastic cup in the vagina with a 5 cm vesico-vaginal fistula at the bladder neck. After trans-vaginal repair, the patient underwent full recovery with an intact continence mechanism. CONCLUSION: Evaluation of unusual urinary symptoms in an adolescent should include pelvic examination and/or imaging. An undisclosed vaginal foreign body is a rare, but well described entity, contributing to vesico-vaginal fistula formation.