Bagley has been involved in family medicine since he was a student at Albany Medical College and served as president of the school's Family Medicine Interest Group. While a third-year resident at St. Joseph's Hospital in Syracuse, he served as chair of the National Conference of Family Practice Residents. In addition to his full-time medical practice, he is a clinical assistant professor at Albany Medical College and Upstate University Medical Center in Syracuse.

In his active leadership role with the AAFP, Bagley has served on numerous commissions and committees in the areas of resident and student affairs, public relations and marketing, member services, and insurance and financial services. He is a fellow of the AAFP, an earned degree awarded to family physicians for distinguished service and continuing medical education. Bagley is also an instrument-rated private pilot and a senior aviation medical examiner.