A 6-year-old female Shih-tzu dog was referred with left elbow joint mass associated with weight bearing lameness. Ultrasonography demonstrated an encapsulated hyperechoic mass at the left elbow joint. Radiography was performed on elbow joint, chest, and abdomen, but there was no evidence of metastasis. Clinicopathologic examination revealed the existence of neoplastic cells with anisocytosis, pleomorphism and increased nuclear-cytoplasmic ratio. The left forelimb was amputated for cure. Histopathological examination diagnosed the mass as a malignant peripheral nerve sheath tumor. During the 4 weeks follow-up, the patient showed full remission and adopted to walk with remaining three legs. Thereafter, the tumor recurred after 5 months of first surgery at the operation site and other two cutaneuos regions. Cytology test revealed the mesenchymal originated tumor cells with malignancy. These tumors were surgically removed and histopathological examination of the resected tissue revealed the recurrence of primary tumor and metastasis. Metronomic therapy with cyclophophamide (10 mg/$m^2$, PO, sid) and piroxicam (0.3 mg/kg, PO, sid) had been adopted for 5 months. At 26 months of follow up after the first surgery, the dog alive with satisfactory quality of life. Aggressive surgical resection with metronomic chemotherapy should be the most effective treatment for malignant peripheral nerve sheath tumor.