Jonathan B. Greer, M.D. earned both his undergraduate and medical degrees from Brown University in Providence, Rhode Island. He completed a general surgical residency at the Massachusetts General Hospital/Harvard Medical School in Boston, a research fellowship in immunology at Memorial Sloan Kettering Cancer Center, and then completed a clinical fellowship in complex general surgical oncology at the University of Pittsburgh Medical Center. After completing his training, Dr. Greer joined Johns Hopkins Medicine in 2018. He was an assistant professor of surgery within the Johns Hopkins Department of Surgery and an assistant professor of oncology within the gastrointestinal cancer program at the Johns Hopkins University School of Medicine's Sidney Kimmel Comprehensive Cancer Center. He was the director of the peritoneal surface malignancy program, program director for the complex general surgical oncology fellowship, and a member of the gastric cancer center, the sarcoma program, and the neuroendocrine multidisciplinary clinic. He was subsequently recruited back to the MGH in March of 2024 to become the program director of the surgical residency and continue to grow the peritoneal surface malignancy program, which, under the leadership of James C. Cusack, Jr., M.D., has been the largest in New England for several years. He is an assistant surgeon at the Massachusetts General Hospital and an Instructor in Surgery at Harvard Medical School.

He is a member of the Association of Program Directors in Surgery, the Association for Academic Surgery, the Trans-Atlantic Retroperitoneal Sarcoma Working Group, the Connective Tissue Oncology Society, and a fellow of the Society of Surgical Oncology (FSSO) and the American College of Surgeons (FACS). He is a member of the scientific advisory board for the Mesothelioma Applied Research Foundation.