We report a comprehensive, longitudinal evaluation of a two-year, part-time postgraduate programme designed to enable health and social care professionals in England to work together to deliver new community mental health services, including psychosocial interventions (PSIs). The study tracked three successive cohorts of students (N = 111) through their learning. Outcomes were assessed according to the Kirkpatrick/Barr et al. framework using a mixed methodology, which employed both quantitative measures and interviews. The students evaluated the programme positively and appreciated its focus on interprofessional learning and partnership with services users, but mean levels of stress increased and almost one quarter dropped out. There was considerable evidence of professional stereotyping but little evidence of change in these during the programme. Students reported substantial increases in their knowledge and skills in multidisciplinary team working and use of PSIs (p < 0.001). Experiences in the implementation of learning varied; in general, students reported significantly greater role conflict (p = 0.01) compared to a sample of their team colleagues (N = 62), but there was strong evidence from self-report measures (p < 0.001) and work-place interviews that the students' use of PSIs had increased. Users with severe mental health problems (N = 72) randomly selected from caseloads of two cohorts of students improved over six months in terms of their social functioning (p = 0.047) and life satisfaction (p = 0.014). Having controlled statistically for differences in baseline score, those in the intervention (programme) group retained a significant advantage in terms of life skills (p < 0.001) compared to service users in two non-intervention comparison groups (N = 133). Responses on a user-defined measure indicated a high level of satisfaction with students' knowledge, skills and personal qualities. We conclude that that there is strong evidence that a well-designed programme of IPE can be effective in helping students to learn new knowledge and skills, and to implement their learning in the workplace. Further, we consider that there is some modest evidence of the benefits of such learning for service users.