Koos Sadie spent 28 years as a professional soldier in the SADF/SANDF from 1974 until 2002. His first seven was in the Infantry Corps, serving in different Infantry Battalions in Namibia and South Africa. In 1982 he started his 21-year intelligence career as a staff officer with the SA Special Forces. He was later appointed as the Chief Instructor at the SA Army School of Intelligence and later to Chief Instructor Intelligence at the South African Army College. Koos Sadie was seconded to the Chilean Army War College, where he functioned as the Chief Instructor for Operations and Tactics. On his return to South Africa, he became the Project Manager for the SA Army War Gaming Centre at the SA Army College. Between 1994 and 2002, Koos Sadie functioned as a Senior Staff Officer Operational Intelligence responsible for the internal covert collection function of the SANDF, reporting to the Chief of Defence Intelligence. After leaving the SANDF in 2002, Koos Sadie became a Project Manager with the National Institute Community Development and Management (NICDAM) and later the Head of the Learner Assessment Centre at NICDAM. In March 2013, Koos Sadie joined Focus Group as the Director of Operations.

Executive director of the Joaquim Chissano Foundation, Chairman of United Bank of Africa and Member of the SADC Mediation Team. Minister of Health 1988 – 1994, Foreign Minister 1994 – 2005. Doctorate (Public Health), member of the Medical Association of Mozambique and Mozambique Medical Council.

A career diplomat, Special Adviser to former President Joaquim Chissano since 2005. He has been involved in special political missions across Africa focussing on Conflict Resolution, Sustainable Development, Accountability and Good Governance.