Dr. Callaghan, a native of Butte, Montana, was raised in and around the Intermountain West. As an undergraduate, he attended Westminster College in Salt Lake City, majoring in biology. While at Westminster, he played on the varsity soccer team. He graduated from the University of Utah Medical School, which was followed by a residency in radiation oncology at the Indiana University Medical Center in Indianapolis. Dr. Callaghan established his practice in Pocatello in 1997.

He is board-certified in radiation oncology and is president of Intermountain Radiation Oncology. He is married to Cheryl Callaghan, M.D., a retired Pocatello gynecologist. The Callaghans have two adult children. He enjoys outdoor recreations. Dr. Callaghan is an advocate of a collaborative approach to the practice of medicine; one that embraces the participation of physicians, support staff, and facilities in optimizing the care of the patient.