Background: Oral Sub Mucous Fibrosis (OSMF) is a clinical entity, well known since the time of Sushruta as 'Vidari'. OSMF is a chronic subtle disease that is associated with significant functional morbidity and an increased risk for malignancy. Generally, OSMF is considered as an adult disease, but recently Indian suburb area has reported incidence of 0.2-1.2 percent in pediatric age group as well. The pathogenesis of the disease is not well established, but is believed to be multifactorial. Areca nut chewing is considered as the major etiology amongst all. Children indulge in habit of chewing areca nuts due to its easy availability of different forms of multicolored attractive areca nut pouches in markets. Other factors involved in the consumption of Areca nut are levels of awareness, household environment, peer pressure, low cost, etc. Case presentation: A 5-year-old boy reported with the complaint of restricted mouth opening since 3-4 months. He had habit of chewing betel nut, a minimum of 2-3 sachets daily since one and a half years. He also complained of intolerance to spicy food. The oral mucosa was pale, opaque, blanched with a reduced mouth opening of interincisal width being 06 mm.Palate was fibrotic with shrunken uvula. Conclusion: This Case of OSMF in a 5-year-old boy is reported to be the first incidence of OSMF in a child with least interincisal opening of 06 mm.