Dr. Jonas undertook his general surgical training in Australia at the Royal Melbourne Hospital and his cardiothoracic surgical training at Royal Children's Hospital in Melbourne and Green Lane Hospital in Auckland New Zealand. He was admitted to the Royal Australasian College of Surgeons in 1982 and subsequently moved to Boston where he undertook fellowships at the Brigham and Women's Hospital and Children's Hospital. He was invited to take a staff position at Boston Children’s Hospital with Dr. Aldo Castaneda in 1984.
In 1994 he was appointed to the William E Ladd Chair of Surgery at Harvard Medical School and became the Cardiovascular Surgeon in Chief at Children's Hospital Boston. In 2004, after 22 years in Boston, he moved to Washington, D.C. where he established the Children’s National Heart Institute which he co-chaired as Chief of Cardiac Surgery until 2020. He maintained NIH supported laboratory and clinical research studies until 2023.
In 2005/6 Dr. Jonas was President of the American Association for Thoracic Surgery. In 2009/10 he was President of the Congenital Heart Surgeon’s Society of North America and from 2016-18 President of the World Society for Pediatric and Congenital Heart Surgery.
Dr. Jonas has a long-standing interest in international education in congenital heart surgery and is currently President of the Global Council for Education in Congenital Heart Surgery. He played a key role in the establishment of the World Journal for Pediatric and Congenital Heart Surgery. His textbook, Comprehensive Surgical Management of Congenital Heart Disease, has been published in several languages and continues to be widely used globally.