The current global situation is imposing increasing demands on stronger innovation capability and increased production capacity and materiel supply. Cross-sector collaboration in the form of triple helix partnerships, i.e., partnerships between government agencies, universities and industry, is considered a successful Swedish concept for researching and developing innovative technology for the Swedish defence. However, previous research on triple helix collaboration in Sweden, including its opportunities and challenges, is limited. This interview study examines four Swedish innovation collaborations involving triple helix actors and how they interact. The aim of the study is to create an understanding of what is required within triple helix collaboration to ensure effective cooperation and, in the long term contribute to increased defence innovation. The study presents the objectives of triple helix collaboration, the roles of the actors and tensions between them, as well as success factors and challenges in triple helix collaboration. The study identifies several challenges related to security classification, public procurement law, intellectual property rights, and balancing political governance and economic mandate. Addressing these challenges is important in order to ensuring effecttive collaboration in defence innovation projects. The study also discusses the policy implications in relation to proposed reforms in the field of defence innovation.