Accessible summary: Psychosocial interventions describe a range of new ways of helping to improve the quality of life of people experiencing psychotic symptoms. The interventions are generally delivered in conjunction with medication used to treat the symptoms.. Research has shown that training nurses and other mental health professionals in these new ways of working makes them more effective when helping people with severe mental health problems. It has also been shown that nurses receiving the training experience lower levels of job-related stress.. In this paper we describe the outcomes of a training programme in psychosocial interventions, which was delivered to both qualified and unqualified nursing staff working in a low secure mental health unit.. Consistent with the findings of previous research the training was shown to lead to positive changes in the nurses' attitudes, knowledge and clinical practice. However, unlike previous studies, the nurses in this study only showed small changes in job-related stress.Psychosocial intervention (PSI) training results in enhanced knowledge, more positive attitudes, increased confidence and lower levels of clinical burnout for qualified mental health professionals and better outcomes for service users who they work with. This paper describes an evaluation of a PSI training course for qualified and unqualified nurses working in a low-secure unit. Forty-two staff (21 qualified) were randomly allocated to an experimental training group or a waiting list control group. Knowledge, attitudes and burnout were assessed before and after the training. In addition, a random sample of 44 care plans written by the qualified nurses were audited before and after to examine evidence of implementation of PSI in practice. Qualified and unqualified nurses in the experimental group showed significant improvements in knowledge and attitudes compared with the control group. Care plans showed a significant increase in the implementation of PSI. The only significant change in burnout was a reduction in depersonalization for qualified nurses in the experimental group. The PSI training may result in improvements in knowledge, attitude and practice in qualified and unqualified nurses working with severely mentally ill patients in low-secure settings, but in this study the training did not incur protection against burnout.