Orbital tumors are rare in dogs. They usually are originated from both mesenchymal and epithelial tissues of the orbit. Osteosarcoma, fibrosarcoma and nasal adenocarcinoma have been related as the most common types of orbital tumors. A 10-year-old male German Shepherd dog was presented to the Spécialité--Diagnóstico Veterinário with left eye disorders such as mucous secretion, divergent strabismus, ventromedial displacement of the ocular globe, conjunctival congestion and positive to the fluorescein test. Ultrasonography of the temporal muscle region was performed. A well-defined, echogenic, diffusely heterogenic, 3.15 cm rounded mass with hyperechoic shadow cast spread in it was found dorsal and lateral to the left orbit. The ocular globe was deformed and medially displaced due to the contact of its caudal aspect with the mass, however others sonographic changes within the globe were not visualized. The lateral aspect of the left orbital bone was intact and preserved. Seven days follow up exam was performed. The mass has increased to 4 cm of diameter. The mass was surgically removed and histopathologically analyzed. At gross the mass was 4 cm of diameter, firmness and white colored at the cut surface with multifocal mineralized areas. The histopathology showed presence of neoplastic osteocytes in a multilobular pattern with anaplastic and multinucleated cells. In addition, it was observed presence of multifocal osteoid production. Three months later the animal presented a similar mass in the contralateral orbit, suggestive of metastasis. Euthanasia was then performed.