AIMS: To explore incentives and barriers to an educational lifestyle intervention for people with severe mental illness. BACKGROUND: Social and lifestyle factors along with long-term antipsychotic therapy contribute to poorer physical health in people with severe mental illness. Behavioural lifestyle interventions for this clinical group have shown some benefit. Evidence relating to the incentives and barriers to interventions is limited. DESIGN: An ethnographic qualitative study was undertaken. METHODS: Data collection was carried out through participant observations and semi-structured interviews with eight mental health service users attending, or previously attended, a group-based lifestyle intervention. Interview data were collected between September 2008-April 2009 and observation data were collected between September-December 2009. RESULTS/FINDINGS: Participant observation highlighted environment, facilitator style, group ownership, group cohesion, information and learning, incentives and barriers as important. Participant interviews identified weight management, social networking, information and communication, role of healthcare professionals and perceived benefits as key themes. CONCLUSIONS: This study provides evidence about the incentives and barriers to lifestyle interventions from service users' perspective, which should inform developments to improve the delivery of lifestyle interventions for this group.