This study aimed to assess whether clinical supervision provided by workplace-based supervisors can enhance outcomes for mental health nurses attending a psychosocial intervention education programme and the service users whom they work with. A quasi-experimental controlled design was used. The main outcome measure was student knowledge and attitudes towards individuals with psychosis and their caregivers. Secondary outcome measures for service users included the KGV (M) symptom scale and the Social Functioning Scale. Students in the experimental group demonstrated a significant increase in knowledge of psychological interventions compared with the control group. Service users seen by the students in the experimental group showed significantly greater reductions in positive psychotic symptoms and total symptoms compared with those seen by students in the control group. Workplace clinical supervision may offer additional benefit to nurses attending psychosocial intervention courses. Further research adopting more robust designs is required to support these tentative findings.