Peripheral cemento-ossifying fibroma is a gingival lesion of reactive nature and unknown etiology. Such a lesion can either interfere with normal tooth eruption or become a factor in plaque development, which usually results in caries formation in newly erupted teeth. Therefore, the objective of the present article was to report a case of peripheral cemento ossifying fibroma occurring in the mandibular posterior region of a 11-year-old girl in association with both absence of premolar eruption and presence of severely caried first permanent molar.