Knowledge sharing is especially challenging when the team is temporary, and time is limited, such as in project teams. Inter-organisational project teams work under high time pressure, which can hinder knowledge sharing beyond organisational boundaries. Adopting a relational perspective on knowledge sharing between teams, we draw on the concept Shadow of the Future, i.e. the positive anticipation of future team relationships, to explain how a positive outlook on future relationships encourages knowledge sharing behaviours in the present. This study conceptualises knowledge sharing as a collaborative task for project teams. Using survey data of 360 projects in China, we study the effect of Shadow of the Future and interactions with time pressure on explicit and tacit knowledge sharing in inter-organisational projects. Results offer important insights on knowledge sharing in inter-organisational project team settings: First, high Shadow of the Future leads to high tacit and explicit knowledge sharing. Second, when time pressure and Shadow of the Future are high, less tacit knowledge sharing occurs between teams than when time pressure is low. However, time pressure is not an obstacle for explicit knowledge sharing. This study extends the current knowledge management literature by offering a deeper understanding of knowledge sharing in inter-organisational project teams. Specifically, we show how team members’ positive outlook on future collaboration influences tacit and explicit knowledge sharing under time pressure in inter-organisational project teams.