Knowledge is a fuzzy phenomenon and managing it a complex endeavor. In particular, knowledge reuse possesses the possibility to increase project performance since project teams can benefit from knowledge of former projects. Therefore, knowledge reuse is an essential knowledge management (KM) process phase that needs to receive special attention. Studying KM in general requires one to consider both social and technical aspects. On the one hand, KM highly depends on individuals, their interactions with each other, organizational rules, and cultural aspects forming KM’s social perspective. On the other hand, contemporary information technologies promise to support organizations, teams, and individuals in managing what they know. Today, the KM research field is tremendous and full of social and technical insights. However, independent of which aspect of KM is studied, most researchers follow either a technology-driven approach for building innovative KM technologies or a behavioral-research approach to observe and understand complex KM phenomena. Few papers report the design of a KM system that integrates the social and technical perspective by expressing and evaluating design principles according the design science research approach. ... mehrIn this paper, we address this challenge and present a comprehensive action design research (ADR) project in the context of managing project knowledge reuse. Thereby, we present our KMS artifact called Just KNow and discuss the entire process from specifying its requirements to its implementation step by step. This paper helps KM researchers and practitioners make informed decisions. We support researchers in deciding whether the ADR approach is appropriate for their particular research project and provide a guideline for how to apply ADR. We support practitioners by helping them make design decisions when creating and implementing an effective KMS.