This article deals with an aspect of the contentious turn the French trade union Force ouvrière (FO) has undergone since the 1980s: the growing importance given by its leaders to interprofessional action. It aims to transcend the idea of a contradiction between confederal discourse and federal practices by taking into account FO’s organizational culture. Structured by federalism and distance from politics, this culture is apprehended through the observation of union training courses. They are described by means of the concept of “group style”. The article shows that training in “thinking interprofessionally” derives from those structural constraints while simultaneously trying to overcome them. Federalism and distance from politics cannot simply be understood as obstacles to the making of a confederal sense of membership. They shape FO’s group style, maintaining the division inside the group as well as the solidness of its outer boundaries. By emphasizing that singularity, the confederal enterprise to reinforce interprofessional identity has less contributed to homogenizing the organization than to developing the confederal scene as a setting for new sorts of activist commitment.