Gingival hyperplasia is a rare condition and is of importance for cosmetic and mechanical reasons. Idiopathic gingival fibromatosis, a benign, slow-growing proliferation of the gingival tissues, is genetically heterogeneous. The enlargement is most intense during the eruption of the primary and permanent teeth, and minimal or nondetectable growth is observed in adults. The genetic aspect, clinical feature, histopathology, immunohistochemistry, and treatment aspects are reviewed. The purpose of this paper was to report a case of idiopathic gingival fibromatosis in a 13-year-old female who had a negative family history for a similar type of gingival enlargement. The diagnosis was established through history, clinical examination, and histopathology using both hematoxylin and eosin and Van Giesen stain (a special stain for collagen). Surgical treatment, which included both gingivectomy and gingivoplasty, was carried out. The case showed remarkable esthetic and functional improvement. The patient returned after a year and showed no recurrence.