Mabel Segun was born in 1930 in Ondo town. Her parents, Reverend Isaiah and Eunice Aig-Imoukhuede were from Sabongidda Ora in Edo State. From 1938 to 1941 Mabel Segun received her primary education in St Peter's School, Edunabon, Akoko Jubilee Central School, Ikare, St Paul's School, Ikole and St David's School, Akure. From 1942 to 1947 she attended the oldest girls' school in Nigeria - C.M.S. Girls' School, Lagos, founded in 1869. She left with a Grade 1 Cambridge School Certificate with exemption from London Matriculation.
Mabel Segun was admitted into the second set of the newly founded University College, Ibadan in 1949 and graduated in 1953 with a second class London Bachelor of Arts Degree in English, Latin and History.
Mabel Segun has had a varied professional career. She has taught in various secondary and post secondary institutions, including Edo College, Benin-City and National Technical Teacher's College, Akoka, Yaba. A trained editor and public relations officer trained in the United Kingdom and the U.S.A., she has also been:
- Hansard Editor to the Western Nigeria Legislature;
- Overseas Publicity and Features Officer, Western Region Information Service;
- Head of Information, Publications and Broadcating, Federal Ministry of Education;
- Pioneer secretary to the Nigerian Book Development Council;
- Deputy Permanent Delegate and Acting Permanent Delegate of Nigeria to UNESCO, Paris;
- Chief Federal Inspector of Education;
- Senior Research Fellow, Institute of African Studies, University of Ibadan and editor African Notes and other Institute publications.
On retiring from both the public service (June 1982) and university service (November 1989), she set up the Children's Literature Documentation and Research Centre (CLIDORC) in Ibadan and became its director.
Mabel Segun has three children, Femi, Gbenga and Omowunmi.