The thesis studies how the transformation of the office influences the construction of an organisation’s identity. More specifically, this research focuses on the introduction of an activity-based workspace, and investigates how the transition towards this new work environment alters the ways of being and of working, and workers’ perceptions of their organisation’s identity. In order to address this question, this thesis is based on a qualitative empirical research in which data were collected through semi-structured interviews, documentary analysis, and observation. Thanks to this empirical design, this thesis shows that the transition towards an activity-based workspace challenges an organisation’s identity, and might result in a fragmentation of the organisational identity among workers, depending on their work identity.