BACKGROUND: Chyle leakage is a well-known complication after thoracic surgery, such as esophagectomy, cardiac surgery, mediastinal lymph node dissection, and neck surgery. However, chyle leakage is a rare complication after dissections of the lateral or subclavian axillary nodes for breast surgery. It is particularly unusual for chyle leakage to occur after minimally invasive dissection of the axillary nodes. Most cases of chyle leakage subside with conservative management, but some cases require surgery. CASE REPORT: An 80-year-old woman had invasive lobular cancer of the left breast (cT1 [1.7 cm], cN0, M0) for which she underwent breast-conservative surgery and biopsy of an axillary sentinel lymph node. Because two of the three sentinel lymph nodes tested positive for cancer, seven lateral axillary lymph nodes (level I) were subsequently removed for the additional sampling. On postoperative day 11, the patient visited our outpatient clinic because of swelling in her left axillary region and breast. Centesis of the axilla yielded 670 mL of milky fluid, which suggested chyle leakage. We commenced the conservative management at first; however, the persistent leakage made us perform the surgical management. The operation was not only ligating the opening of the chyle duct but needed total mastectomy because the postoperative pathology report showed invasive lobular carcinoma; the nipple and the caudal surgical margin of the lumpectomy were positive for cancer. The patient agreed to our recommendation of total mastectomy and surgical management of the chyle leakage. Ligation of the opening completely resolved the chylous discharge. CONCLUSION: We here report a case of large-volume leakage of chyle after sampling dissection of the lateral axillary lymph nodes for left breast cancer; the leakage persisted despite the standard conservative therapy but was resolved after surgical treatment. Chyle leakage can occur even after minimally invasive dissection of the axillary nodes.