Knowledge management encourages organizations to create and use knowledge continuously to gain competitive advantage. Some knowledge management approaches are industry specific, theoretical and procedure-wise without consideration of system interoperation. The lack of interoperability means heterogeneous systems from different organizations are unable to communicate, cooperate, exchange, and reuse knowledge with one another. Thus a collaborative interorganizational network is necessary. In this paper, we propose the use of ontology for organizations to access and retrieve inter-organizational knowledge in a similar domain. The incorporation of ontology and its mediation methods in the network allows organizations to reuse the interorganizational knowledge to support individual organizational knowledge management processes. A case study illustrating ontology-based collaborative inter-organizational knowledge management network over publication services among universities and business sectors is included.