BACKGROUND: Users with mental health problems (users) have a substantially higher risk of developing type 2 diabetes than the general population. Recent studies show that traditional lifestyle interventions focusing solely on exercise and diet among users have limited effect. Studies suggest collaborative models as a starting point for health behaviour change are more beneficial, but implementation in practice is a challenge. Using the Medical Research Council's guidance for process evaluation, we explored implementation of a collaborative model in health education activities targeting users. The collaborative model focused on involving users in agenda setting and reflection about readiness to change health behaviour and was supported by dialogue tools (e.g., quotes and games). Educators received 3 days of training in applying the model. METHODS: Collected data included questionnaires for users (n = 154) and professionals (n = 158), interviews with users (n = 14), and observations of health education activities (n = 37) and the professional development programme (n = 9). Data were analysed using descriptive statistics and systematic text condensation. RESULTS: Ninetysix percent (152) of professionals tested the model in practice and tried at least one tool. Users reported that the model supported them in expressing their thoughts about their health and focused on their needs rather than the agenda of the professional. Ninetythree percent (143) of users strongly agreed that professionals were open-minded and responsive. However, observations showed that some professionals overlooked cues from users about motivation for health behaviour change. Furthermore, professionals identified lack of involvement from their managers as a barrier to implementation. CONCLUSIONS: Implementation of a collaborative model was feasible in practice. Training of professionals in active listening and involvement of managers prior to implementation is crucial.