Prof Mariba was appointed as the first dean of the newly established Faculty of Health Sciences in 2001. He was elected to various leadership positions including:
• President of the Committee of Deans of Medical Faculties of South Africa
• President of the Health Professions Council of South Africa and a member of the Senate College of Medicine of South Africa
• Chair of the Medical and Dental Professions Board of South Africa
• President of the Association of Medical Councils of Southern Africa
• Chair of the International Association of Medical Regulatory Authorities
• Member of the Council of the University of Pretoria
• In 2004 he received a Fellowship of the Royal College of Physicians.