Gynecomastia is defined as benign proliferation of glandular breast tissue in men. Physiologic gynecomastia is common in newborns, adolescents, and older men. It is self-limited, but can be treated to minimize emotional distress and physical discomfort. Nonphysiologic gynecomastia may be caused by chronic conditions (e.g., cirrhosis, hypogonadism, renal insufficiency); use of medications, supplements, or illicit drugs; and, rarely, tumors. Discontinuing use of contributing medications and treating underlying disease are the mainstay of treatment. Medications, such as estrogen receptor modulators, and surgery have a role in treating gynecomastia in select patients. Treatment should be pursued early and should be directed by the patient.