The ameloblastic fibro-odontoma (AFO) is a rare odontogenic tumor that occurs predominantly in children and is generally associated with unerupted teeth. The choice of treatment for this entity is conservative surgery with enucleation and its prognosis is excellent. However, preserving the associated impacted teeth may make complete removal of the lesion difficult and may explain some cases of recurrence. A case of AFO in a 6-year-old girl treated with enucleation and preservation of an impacted lower left first permanent molar is reported. After two years of follow-up, there were no signs of recurrence and complete spontaneous eruption of the preserved tooth was observed. The present report indicates that the degree of involvement of the impacted tooth by AFO is a fundamental aspect to be considered during radiological analysis and surgical assessment. We concluded that preservation of the impacted permanent teeth associated with this tumor should always be considered and carried out with caution, since they are clearly not included in the surgical cavity. (J. Oral Sci. 49, 331-335, 2007)