Cultural Heritage Projects (CHP) are complex activities involving multiple and heterogeneous actors trying to align their different and diverse ontological and epistemological perspectives and, at the same time, trying to get coordinated and share knowledge about heritage objects, among an incommensurable diversity of related data, information, and knowledge, and including information technologies for coordination. In this context, the socio-technical approach to designing information systems has become prevalent but contradictory in knowledge coordination scenarios in which heritage experts and coordination technologies act as inseparable sociomaterial assemblages that evolve through routines and affordances, depending on contextual dimensions of particular projects. By grounding this work on a design science approach, the paper presents the sociomaterial design of a Knowledge Management System (KMS) for cultural heritage projects, aimed at overcoming coordination issues for sharing knowledge within and between heritage projects. Evaluation results outline that knowledge access and visualization, flexibility in sharing practices, and decision-making issues can be enabled by using the KMS. The proposed system has been designed from the particularities of an international knowledge sharing network and brings forward novel design and coordination insights, which could be successfully deployed in heritage projects and networks with similar coordination and collaborative features.