Open Innovation (OI) revolves around the idea that to survive, organisations must identify, plug into, and leverage external knowledge sources as a core process in innovation. The creation and guarding of a suitable level of organisational permeability in the daily practice of OI can be challenging for both individuals and organisations as innovation processes also require openness as a social attitude. Looking at OI as real life multi-layered practices that are performed through talk and interaction, this dissertation examines how openness in OI is enabled through languaging. Close investigation of three industry-academia cases has shown that collaborators use interactional strategies to negotiate the extent of openness in meetings, to stimulate fearless knowledge sharing and to build and rebuild interpersonal relations and identities. While project work is laced with misunderstandings and negative perceptions on the one hand, openness and transparency are also highly valued by individuals on the other hand. When individuals have awareness of and ability to choose from a variety of linguistic options contingent on the social dynamics in the collaboration, this can further shape a knowledge-sharing-friendly atmosphere in which academics also feel free to pursue their own agenda. Through connecting the marco-environment and the micro-practices of the cases, it has become possible to integrate the rapidly changing context of industry-academia collaboration as a dynamic factor and to evaluate OI by the actualisation of its linguistic practices in its own regard. Hence, this dissertation describes the social, interactional and contextual boundaries of openness and shows how the linguistic choices that individuals make, enable OI as collaborative knowledge work beween industrials and academics.