Project management involves many different actors. Rather than solely looking at those actors as individuals, the interaction between them should not be forgotten either. This thesis tries to provide a better understanding of one specific type of interaction: the project owner-manager relationship. This relationship is approached as the dyadic interaction between one project manager and one project owner. Previous studies indicate that project owners and project managers depend on one another, but that they can have diverging perspectives as well. The goal of this study is to get a deeper understanding of how these different perspectives can influence the success of the project-owner relationship. In order to achieve this understanding, a multiple case study involving 8 project owner-manager relationships was employed. Both project owners and project managers were interviewed, in order to get closer to a multi-actor perspective. The results show that there are both similarities and differences between the perspectives of these actors. However, a lack of understanding between these perspectives can cause the project owner-manager relationship fail. In the end, the potential effects of this relationship cannot and should not be ignored, as this study shows that it can be the difference between project success and project failure. Therefore, in a world that is ever more dominated by projects, this thesis has multiple practical and scientific implications.