The notions of Operational Leeway and Power to Act have been widely developed in recent years, particularly, in the fields of ergonomics and psychology. The intuitiveness of these notions has led to a generalization of their use in clinical approaches to work activity, especially, in relation with the prevention of musculoskeletal disorders or psychosocial risks. However, because this generalization was not always supported by conceptualization efforts, it has led to confusions and inaccuracies in both scientific exchanges and professional debates among ergonomists and psychologists. In recent years, increasingly frequent contacts between activity ergonomics and occupational psychology – more specifically, the clinical psychology of work – has made this lacuna more evident. Accordingly, the authors of the present article, all of whom are ergonomists, propose a theoretical articulation of the concepts of Operational Leeway and Power to Act. The main implications of this model for ergonomic intervention are then developed.