Collaborations are particularly important for the development and deployment of technology. We analyze the influence of organizational, technological and geographical proximity on European nanotechnology collaborations with the help of a publication dataset and additional geographical information. While organizational proximity influences collaboration only indirectly geographical and technological proximity do so directly. Geographical proximity is most significant in statistical terms and technological proximity has the highest magnitude of effect. Consequently, the latter lends itself most for management and policy interventions, e.g. providing information on technological specialization of potential partners or on project management tools.