Multiple myeloma is a monoclonal malignant proliferation of plasma cells that causes osteolytic lesions in the vertebrae, ribs, pelvic bone, skull and jaw. We report a case of a 66 year-old-woman with pain and right facial swelling. Radiographic examination showed a well-defined radiolucent lesion in left posterior mandible. An incisional biopsy was performed and histopathological examination revealed proliferation of malignant plasma cell with off-center and hyper chrome nucleus. The results of biopsy, imaging, and laboratory investigations led to the diagnosis of multiple myeloma. This maxillofacial manifestation of multiple myeloma is not that rare, but dentist knowledge about maxillofacial manifestation can help in early diagnosis and consequently better prognosis of the disease.