Persons with severe mental ill-health die early from preventable physical ill-health. Registered nurses in psychiatric outpatient care play a key role in improving persons’ physical health, and it is important to examine how they view their responsibility, their experiences of care, and the obstacles they meet in providing person-centred care. The purpose of this study was to explore registered nurses’ experiences of caring for persons with mental ill-health and somatic comorbidity in psychiatric outpatient care, using qualitative content analysis to analyze data from semi-structured interviews. The results show that these nurses monitored the person’s right to equal care, embraced the whole of the persons suffering, and dealt with unclear boundaries in care. This highlights the unique role that registered nurses play in psychiatric outpatient care via their ability to interpret symptoms and find ways to adapt care based on persons’ needs. Registered nurses consider physical health in all care and provide a link between psychiatric and somatic care. Together with mental health nurses at primary health care centers, they are key in reducing persons’ suffering. There is a need for structural and functional changes in line with person-centred care including collaboration both within and outside healthcare organizations.