Granular cell tumors (GCTs) are rare benign soft tissue tumors that can occur throughout the body, particularly the head and neck; only 5%-8% of GCTs occur in the breast. We report a case of a GCT of the axillary accessory breast, which is a rare location of this tumor. A 50-year-old woman had a 2-month history of a palpable mass in the left axilla. Physical examination, as well as mammographic and ultrasonographic findings suggested a breast malignancy. Histopathological examination showed a benign GCT, and wide local excision was performed. The patient has remained disease-free over 2 years postoperatively. Although most GCTs are benign, wide complete resection of the tumor and follow-up are required considering the possibility of recurrence. The radiologist should know the characteristics of GCTs as a differential diagnosis of breast and axillary lesions to prevent unnecessary treatment.