The Johannes Zimmermann library of ACI is a reference library that serves the Institute’s academic and pastoral programmes and its research projects. It is also open to visiting academics and students, Christian workers and others interested in researching in its areas of specialisation.

The library specialises in mission history and the history and theology of the church in the non-Western world generally, with a particular interest in the church in Africa and especially Ghana. Holdings include a collection of writings in Ghanaian languages dating from the mid-19th century, as well as studies in history, religion and culture. Inter-religious engagement is a further area of specialisation with a recently acquired up-to-date PhD level collection in Islamic studies. Modern biblical, theological and pastoral literature for the benefit of Christian workers is also available. A notable feature is the growing collection of journals from around the world, which gives access to the latest Christian thought and practice in mission. Library holdings (now over 20,000 books) are computerised.

The Institute has on microfiche the important collection of materials from the Institute for the Study of New Religious Movements, Selly Oak, Birmingham, UK, and has plans to expand its microfiche collection with materials relating to Africa from missionary society archives. The Institute also holds on microfilm the early Basel Mission records on Ghana.

Archival holdings include books from the 19th century Basel Mission library at Odumase-Krobo and collections of old books and manuscripts from the libraries of notable Christian families in Ghana, including the papers and manuscripts of Dr. C.A. Akrofi, books belonging to Rev. David Asante, the first ordained Ghanaian minister of the Basel mission Church, the library of the late Rev. E.M.L. Odjidja (former Moderator of the PCG) and the papers of the late Dr. Ephraim Amu.

Library facilities comprise a main reading room, a reference and periodicals reading room, study carrels, computer and microfilm/microfiche facilities, and archives. The Institute also has access to the Internet.
As the Institute is expanding and its student population is growing, a new, purpose built library building is under construction. This will be a three-storey building with extended basement, comprising a reference/periodicals floor, with additional exhibition/lecture room, a main holdings/reading room/study carrels floor and an archive/audio-visual floor. Library offices will also be provided on each floor.