The lower labial frenum attached to the free gingival margin can promote local tension, resulting in tissue ischemia, promoting the development of gingival recession, as well as complicating oral hygiene, resulting in chronic inflammation. In this case, early diagnosis and surgical treatment is recommended. This is the case about surgical treatment of heavy mandibular labial frenum in pre-school child with a history of syndactyly surgery. A 5-year-old girl visited the clinic with the chief complaint of high labial frenum of the mandible. Hyperplastic lower labial frenum was attached to the free gingival margin on the primary mandibular lateral incisor area. After fifteen month follow-up, right after the eruption of the permanent lower right lateral incisor, 6 years old patient received lower labial frenectomy to prevent periodontal diseases in permanent teeth and to reestablish normal anatomic characteristics. After 2 years of follow-ups, there were no marked complications.