What difference do we make between Leroy Merlin, Castorama or Bricorama? These organizations are distinguished by a set of attributes that shape their uniqueness, their identity. This research proposes to better understand how organizational identity is formed. The identity question is addressed by taking a strategy as a practice lens and is grounded in organizational identity theory. In order to answer the research question, the thesis is interested in the role of the stakeholders, practices and materiality on the organizational identity formation process. The originality of this work lies in the study of identity formation from inception of an innovative intermediary in the construction sector. The research is based on a unique longitudinal case with an ethnographic dimension. It includes a survey of the perception of external stakeholders about the organization’s identity.The results highlight the preponderant role of founders but also of employees in identity formation. The case of an innovation intermediary reveals a strategy to form organizational identity: organizational identity play. It corresponds to the exploration of several possible futures. In addition, three practices for "forming, repairing, maintaining, strengthening, or revising" identity are highlighted. Finally, the results highlight the effects of the absence of an artifact (a physical platform) that contributes to exacerbate conflict over identity among members.