Granulocytic sarcoma (GS) is a localized infiltrate of immature granulocytes in an extramedullary site. This lesion is most frequently associated with leukemia, but can occur associated with other myeloproliferative disorders. GS can affect virtually any part of the body, but oral lesions are rare, with only 37 cases described. METHODS We present a case of GS in a 23-year-old female, with a prior history of acute myeloid leukemia, presenting with a solitary mandibular swelling in the region of the erupting lower left 3rd molar. After biopsy, conventional immunohistochemical stains were positive for CD45 (hematological marker) and myeloid markers, such as myeloperoxidase, and CD68, demonstrating a myeloid lineage with monocytic cell differentiation, suggesting the diagnosis of GS associated to AML-M5. CONCLUSIONS Although GS is a rare tumor in the oral cavity, and its diagnosis is usually difficult, the clinician must know of its existence in order to make a differential diagnosis.