Background Suicide is the leading cause of avoidable death in prisons worldwide and suicide prevention is an international priority. Consequently, there is an urgent need to develop evidence‐based treatments. We conducted a randomized controlled trial of a novel suicide prevention psychological therapy for male prisoners. To promote ecological validity by addressing the “real‐world” situation of suicidal prisoners, we involved a consultant group of ex‐offenders with past experience of being suicidal during imprisonment. Service user involvement in prison research is challenging and underdeveloped. Objective We aimed to investigate the ex‐offender service user consultants’ experiences of being involved in the research. Design Individual qualitative interviews were conducted and analysed using an Interpretative Phenomenology Analysis (IPA) framework. Setting/participants The study was conducted at a university in North England, UK, comprising four ex‐offenders with experience of being suicidal during past imprisonments. Results Two superordinate themes were identified: “Working Together” depicted participants’ perceptions of the pivotal role of good relationships with researchers, and “Journey of Change” outlined how participants’ involvement in the research impacted on their personal lives. Discussion Little is known about how to successfully involve ex‐offender service users in research. Our results indicate the conditions necessary for successfully engaging ex‐offender service users in research and have important implications for improving the quality of prison research. Conclusions Involving forensic service users in research is feasible and should be encouraged, as despite certain challenges, it is highly rewarding both for the research and the ex‐offender service users.