More than 12% of women will be diagnosed with breast cancer at some point in their lives, and 78% of them can be expected to survive for at least 15 years. More than 2.8 million breast cancer survivors currently reside in the United States. After breast cancer treatment, as many as 90% of survivors report physical problems that can reduce functional ability, produce or exacerbate emotional problems, negatively affect body image, and diminish quality of life. Many survivors will seek care for late and long-term effects of treatment, which will not necessarily be recognized as such by health care providers and appropriately treated. In this article, the authors discuss the underlying causes of late and long-term sequelae of breast cancer treatment and describe effective assessment and management strategies. They focus specifically on the most common and potentially debilitating upper body effects of breast cancer surgery and external radiation therapy: lymphedema, axillary web syndrome, postmastectomy pain syndrome, rotator cuff syndrome, adhesive capsulitis, arthralgias, cervical radiculopathy, and brachial plexopathy.