Odontoameloblastoma is an extremely rare tumor derived from odontogenic epithelium and mesenchyme. In the fewer than 20 reported cases, odontoameloblastoma is described as occurring in the maxilla or mandible of young men with a history of unerupted teeth. Here we report a case of a 73-year-old woman who presented to the dentist for routine cleaning and x-rays, which displayed a mandibular lesion. After referral to multiple providers, a biopsy of two involved teeth was obtained and computed tomography of the neck was performed, revealing a large, destructive lesion of the mandible. Histology was consistent with odontoameloblastoma. The patient underwent wide segmental mandibular resection and scapula tip free flap reconstruction. She recovered uneventfully and continues to have close follow-up, given the risk of recurrence. To the best of our knowledge, this is the first reported case of odontoameloblastoma in a patient over age 50. The goal of the authors is to raise awareness of this rare pathology and its diagnostic and management modalities.