Idiopathic gingival fibromatosis is a rare condition in which the gingival undergoes a benign fibrous hyperplasia. The correct diagnosis is based on clinical findings, history, and histological examination. The lesion may occur locally or generally and usually presents with the eruption of the primary or secondary dentition. The best timing of treatment is after the period of puberty. The lesion of this patient is diagnosed as idiopathic gingival fibromatosis because the etiology is obscure. There was nothing of relevance in her medical or family history. The excessive gingival tissue was removed by gingivectomy and gingivoplasty. One year follow-up revealed stable condition without recurrence.