The focus was to describe Swedish psychiatrists' experiences of collaboration with healthcare professionals when treating women with postpartum psychosis (PPP). A qualitative design was used, and semi-structured interviews were performed with nine psychiatrists working in psychiatric hospitals in Sweden. Data were analysed using manifest and latent content analysis. The results of these experiences were categorized in this study as: collaboration related to admission, collaboration during inpatient care and collaboration related to discharge. Collaboration with midwives and obstetricians was important in diagnosing the illness, as this often occurred on postnatal wards; and decisions about the form of care for the woman with PPP and for her baby demanded collaboration with various healthcare professionals. Collaboration with nurses was based on expectations and confidence in nurses' competence, and was exceedingly important during inpatient care. When the woman was to be discharged, collaboration with healthcare teams, e.g. outpatient clinic, child health clinic and community services, was required. The conclusions were that psychiatrists collaborate with different professionals in the various phases of the caring process. They rely extensively on nurses' competence when caring for women with PPP, and consider nurses to be their most important collaborators.