Upper arm pain in the armpit six months after breast conserving surgery may be caused by scar contracture, nerve injury, recurrence of disease and so on. 1. Scar contracture: due to the gradual formation of incision scars, which leads to scar contracture, scar pulling pain may occur when lifting the upper limbs or performing exercise. 2. Nerve damage: a common complication of breast cancer surgery, it may cause damage to the axillary artery and the nerves in the axillary sheath, thus causing neuropathic pain. 3. Disease recurrence: it may also be due to the patient’s metastasis or recurrence after surgery or within a short period of time, resulting in localized upper limb or axillary metastasis, which leads to axillary upper arm pain after six months of breast-conserving surgery. If the symptoms of axillary upper arm pain after six months of breast-conserving surgery persist without relief, timely medical treatment is needed.