A 62-year-old woman with triple-negative breast cancer underwent breast-conserving surgery followed by adjuvant chemotherapy and radiotherapy to the breast. The patient developed a solitary lung metastasis at the left hilum 44 months after the operation. The lung metastasis responded partially to capecitabine chemotherapy, but showed regrowth in 7 months. The patient received second-line oral cyclophosphamide (CPA) chemotherapy, resulting in marked tumor regression without new lesions for 10 months. To further control the lung metastasis, stereotactic body radiotherapy (SBRT; 5.1 Gy ×10 fractions) under breath holding without a localization device was given to the regressed lung metastasis after CPA therapy. Positron emission tomography at 24 months after the completion of SBRT did not show any recurrences, and the patient has been well for 100 months without any recurrences. Breast oncologist should take SBRT into consideration to treat lung oligometastasis of breast cancer especially locating at the lung hilum with curative intent.