Health policy is increasingly advocating for involvement of service users and family members in service development. In the present study, we evaluated the impact of a 4-day education programme in co-facilitation skills on clinician and peer (service users and family members) knowledge, confidence, and subsequent experience as co-facilitators. The programme was designed to train peers and clinicians as co-facilitators on a clinician and peer-led information programme for people experiencing mental health problems. The study employed a mixed-methods design involving a pre-post survey with 128 participants, and follow-up qualitative interviews with a sample of 17 participants. To examine changes in levels of knowledge and confidence in facilitating from time 1 (T1) to time 2 (T2), paired sample t-tests were conducted, and thematic analysis was conducted on the interviews. The programme had a statistically-significant positive impact on participants' knowledge, confidence, and skills, with no significant difference between the facilitator groups (i.e. service user, family member, and clinician) in terms of their improvement at the end of the training, indicating that all groups benefited equally from the training. A majority of participants reported a high level of preparedness as co-facilitators and an open and respectful approach towards each other's expertise, and many continued to gain skills and develop their confidence as they co-facilitated the 8-week EOLAS programme ('eolas' is the Irish word for knowledge). The findings also provide evidence of the acceptability and feasibility of the programme, and appears to be the first detailed study reported on a programme of this nature.