Psychologists in hospital settings are part of a complex network of professional relationships in constant negotiation. In addition, psychologists have skills that enable them to work with social phenomena and to act strategically within them. This is especially important in inter-disciplinary team work where professional boundaries can generate barriers to change. This article shows how psychologists of a maternity hospital in a working-class district of a large Brazilian city adapted to an integral approach to health care in a way that helped other professionals to rethink practices.