Following an internship and residency at Massachusetts General Hospital (MGH), he became a clinical associate at the National Institute of Arthritis and Metabolic Disease (NIAMS) where, under the guidance of Ed Rall, he studied the effects of androgens on thyroid function, thyroxine metabolism, and thyroxine-binding protein.
In 1957, he began a two-year clinical research fellowship with Sir Edward Pochin at the University College Hospital Medical School, London, pioneering in the use of radioactive iodine for the treatment of thyroid cancer.
From 2000 to 2007, Federman was senior dean for alumni relations and clinical teaching at Harvard Medical School.
[9] As a medical student at Massachusetts General Hospital in Boston, Federman met his wife Elizabeth (Betty) Buckley.
He was an avid sailor and enjoyed classical music, having contributed to the work of the Longwood Symphony Orchestra in Boston.