Interdisciplinary collaboration is often highlighted in official discourses and represents a considerable challenge for organisations, universities and schools. To address this challenge, proximities/distances, knowledge boundaries and boundary objects are useful concepts to analyse the obstacles facing interdisciplinary collaboration, and to identify levers to cross the knowledge boundaries between disciplines. We raise two research questions. Why is it so hard to work together and collaborate in an interdisciplinary context? How can interdisciplinary collaborative work be sustained? To answer these two questions, we mobilise the literature on the subject and analyse the case of ALLIBEAS. The study highlights three main findings. Cognitive and institutional distances and collective tacit knowledge create knowledge boundaries that make collaboration difficult. Geographical, social and organisational proximities facilitate interdisciplinary collaboration, but are not sufficient. Some micro processes and artefacts are needed to make students from different disciplines and schools interact, create social links, and cross knowledge boundaries.