A 3-year-old female spayed Australian Shepherd mix dog was presented to the Cornell University Hospital for Animals Emergency and Critical Care Service following first observation of an oral mass. Aside from an oral mass, the patient was clinically stable with the remainder of the general physical exam unremarkable; she was referred to the Dentistry and Oral Surgery Service for further evaluation. Oral exam revealed a 4.9 x 4.0 x 2.0 cm pedunculated, bilobed mass arising from the right caudal maxilla. Initial diagnostics included complete blood count and chemistry panel, intraoral radiographs, and wedge biopsies. Histopathology revealed features consistent with a fibrosarcoma. Staging and surgical planning diagnostics included: 3-view thoracic radiographs, abdominal ultrasound, bilateral fine needle aspirates of mandibular lymph nodes, and a computed tomographic (CT) scan of the head. There was no evidence of tumor metastasis and CT indicated a focal area of bone lysis palatal to maxillary teeth 108 and 109 with minimal neoplastic invasion into the nasal cavity. A caudal maxillectomy was performed without complication. Histopathology indicated one narrow to incomplete surgical margin at the dorsal medial aspect at the junction with the bone of the nasal cavity. At two weeks post maxillectomy the surgical site was completely healed and the patient had returned to normal activity and diet with no evidence of local recurrence. The client declined adjunctive radiation therapy at that time and elected to monitor for local recurrence.