We argue that successful participatory mental health organisations should be seen as ‘engines of alternative objectivity’ rather than as the subjective ‘other’ to objective science. With the term ‘alternative objectivity’, we point to collectivisations of experience that are different to biomedical science but are nonetheless forms of objectivity. Taking inspiration from feminist theory, science studies and sociology of culture, we argue that participatory mental health organisations generate their own forms of objectivity through novel modes of collectivising experience. Through two case studies, the Hearing Voices Movement and Stepping Out Theatre Company, we demonstrate how successful participatory organisations can be seen as ‘engines of alternative objectivity’ rather than as the subjective other to objective, biomedical science. The Hearing Voices Movement cultivates an ‘activist science’ that generates an alternative objective knowledge through a commitment to experimentation, controlling, testing, recording and sharing experience. Stepping Out distinguishes itself from drama therapy by cultivating an alternative objective culture through its embrace of high production values, material culture, aesthetic standards and critical review processes. A crucial aspect of participatory practice is overcoming alienation, enabling people to get outside of themselves, encounter material worlds and join forces with others.