In 1967, he assisted his brother Christiaan, during the first successful heart transplant, a procedure which now saves thousands of lives around the world each year. While performing life-saving operations in South Africa, Dr. Barnard found it difficult to accept that his patients were, in many cases, unable to return to employment for health reasons, and that their families often suffered tremendous financial hardships.

In 1983, Dr. Barnard developed the world's first Critical Illness Insurance (CII) policy in conjunction with an insurance company in South Africa. The product is now available in many countries around the world including Australia, Canada, Ireland, Japan, South Africa, and the United Kingdom. Dr. Barnard continues to help introduce this leading-edge product to consumers in the United States and other parts of the world as well.

Today, Dr. Barnard leads the world in developing insurance policies that help patients better cope financially after a traumatic illness. An international speaker, Dr. Barnard has been published extensively on both medical and non-medical topics.

In 1976, Marius Barnard became associate professor in the department of cardiac surgery at the University of Cape Town. He is a fellow of the American College of Surgeons, and the American College of Cardiologists. In 1966, he won the George Sacks Award for surgical research.