This article examines how mediators contribute to formulating a particular type of interactivity by bringing to the forefront institutionally appropriate identities of participants. An existing collection of 18 transcripts from audio recordings of mediation sessions at a mediation center in the western United States serves as a source of interactional data. The study shows that mediators act as designers to construct mediation as a collaborative activity. They invoke identities as an exercise in articulating what is possible in this interaction and exerting control over interactants. Mediators are not just doing what is appropriate for this institutional context; their actions are an act of constructing identities out of what is available there. Participants can act in different ways (e.g., as an ex-husband and an ex-wife). However, relative to the institutional agenda of the meeting, they are encouraged to perform in the capacity of parents and to be collaborators.