ABTAPL has both individual and institutional members.

Its individual members often have a professional connection to libraries of philosophy or theology. The institutional members, of which there are nearly eighty, include theological colleges as well as independent libraries and academic and research libraries with collections in philosophy or religion. Some members are in Ireland and mainland Europe as well as within the UK. The association organizes training events and an annual conference.

There is more information on the history of the organization here.