Researchers have developed various knowledge management approaches that only focus on managing organizational knowledge. These approaches are developed in accordance with organizational KM strategies and business requirements without the concern of system interoperation. The lack of interoperability means that heterogeneous Knowledge Management Systems from different organizations are unable to communicate and integrate with one another, this results in limitation to reuse inter-organizational knowledge. Here, inter-organizational knowledge is defined as a set of explicit knowledge formalized and created by other organizations. In this research, a collaborative inter-organizational KM network is proposed to provide a platform for organizations to access and retrieve inter-organizational knowledge in a similar domain. Furthermore, ontology and its related mediation methods are incorporated in the network. The concept of ontology enables organizations to explicitly represent their knowledge of a specific domain with representational vocabulary in terms of objects and their interrelated describable relationships. Although different organizations may possess their own set of ontologies, the mediation methods that include mapping, merging and integration are capable of reconciling the underlying heterogeneities of ontologies. In this way, it is possible for the participant organizations to reuse inter-organizational knowledge within the network even though there are fundamental differences among organizations in terms of KMS structures and knowledge formats. The retrieved inter-organizational knowledge could then be used to support knowledge creating, storing, dissemination, using and evaluation of the organizational KM process. In additional, a selection framework is also proposed to assist organizations in choosing suitable ontology mediation approaches, ranging from mapping approaches. levels of automation, mediation methods to matching techniques. While knowledge engineers could reuse inter-organizational knowledge to create and evaluate organizational knowledge, general users are benefit from the effectiveness and efficiency in searching for relevant inter-organizational knowledge within the network.