BACKGROUND: : Service user involvement has become increasingly prioritised within health research, and more recently, within mental health and psychosocial support (MHPSS). However, there is limited exploration of service user involvement in the development of lay-delivered MHPSS psychological interventions. The aim of this research was to investigate how service users have been involved in the development of lay-delivered psychological interventions for populations affected by humanitarian crises. METHODS: : Thirteen semi-structured interviews were conducted with respondents involved in randomized controlled trials (RCTs) of lay-delivered MHPSS psychological interventions, either as principal investigators or as focal points for service user involvement. Thematic data analysis used was used to analyse the data. RESULTS: : There was a common perception that service user involvement is vital to the development of lay-delivered psychological interventions, but there was concern about how that happened in practice. Respondents desired to increase service user involvement, but they either did not know how to do this into practice or felt that they lacked the resources to do so. Recommendations were made for strengthening involvement, such as employing service users onto research teams. However, legal difficulties in compensating service users for their work were raised. CONCLUSION: : Service user involvement was viewed as vital in the development of lay delivered psychological interventions, but remains predominantly tokenistic, partly due to limited guidance, time, and finances. Guidelines could support more meaningful and ethical service user involvement in lay-delivered psychological interventions in areas affected by humanitarian crises.