Kabbah's background is a mixture of politics and technical work. He joined the SLPP in 1954. Upon completing his education abroad, he returned to Sierra Leone to serve as a district commissioner in the Moyamba, Kono, Bombali, and Kambia districts (thus having served in each of the country's major regions). He later served as a deputy secretary in the Ministry of Social Welfare and as the permanent secretary in charge of both the Ministry of Education and the Ministry of Trade and Industry. As the Stevens government became increasingly insular during the early 1970s, Kabbah sought administrative work outside of Sierra Leone with the United Nations. He first worked as a deputy chief for the UN's West African division, and then served as a United Nations Development Program (UNDP) representative to Lesotho (1973), Tanzania and Uganda (1976), and Zimbabwe (1979). In 1979, he became the chief of the UNDP eastern and southern African divisions, where he was directly responsible for assistance to liberation movements. Two years later, he became a UN director for administration and management.
Kabbah's work in Sierra Leone resumed when he was selected to chair an advisory council formed to review the 1991 Constitution. His intimate knowledge of the Constitution, combined with his extensive experience in national and international administration, was a major factor in his selection as the SLPP presidential candidate in the 1996 elections.