Inter-organisational projects are becoming more common across various industries and attract increasing attention due to their flexibility to cope with changing society and unique challenges in time, task, team, and transition. Collaboration, as a crucial role in project management, becomes significantly challenging and important under such circumstances. Collaboration serves as a strategy to not only overcome persistent challenges in project but also navigate uncertainty and adapting to change. However, real collaboration remains difficult to implement, and digital transformation presents new opportunities to enhance collaboration. Meanwhile, successful digital transformation also relies on strong collaboration since its implementation requires multi-disciplinary cooperation, shared understanding, and trust among participants. This paper outlines the research proposal for the researcher’s PhD project, which aims to explain how collaboration and digital transformation influence mutually in inter-organisational projects.