Lymphedema is a feared complication of cancer treatment and one that negatively impacts survivorship. The incidence of breast cancer-related lymphedema ranges from 6% to 70%, but lymphedema may be a common and under-reported morbidity. No standard guidelines for its diagnosis and assessment exist. Although the true etiology of lymphedema remains unknown, radiation, chemotherapy, type of breast surgery, and extent of axillary surgery are commonly cited risk factors. However, the relationship between the number of nodes removed and the risk of lymphedema is not clearly correlated. Clinical trials are focusing on ways to reduce the need for axillary dissection even in the setting of a positive sentinel node, to help minimize axillary morbidity. Risk-reduction practices, including avoidance of skin puncture and blood pressures in the ipsilateral upper extremity, and precautionary behaviors such as wearing compression garments during air travel continue to be advocated by the medical and survivor communities, despite a lack of rigorous evidence supporting their benefit. Emerging data support exercise in at-risk and affected women with lymphedema when started gradually and increased cautiously.