We report the CT and MR imaging findings of a case of a desmoplastic fibroma of the mandible in a 6-month-old girl who presented with a rapidly enlarging facial mass and who represents one of the youngest reported children with this rare tumor. Although imaging is non-specific and these lesions are best distinguished histologically, the desmoplastic fibroma should be considered when there is an occurrence of any bubbly or cystic expansile mandibular lesion presenting in childhood.