BackgroundRefugees are at an increased risk of developing symptoms of mental disorders but face various structural and socio-cultural barriers to accessing mental health care. The SPIRIT project (Scaling-up Psychological Interventions in Refugees In SwiTzerland) seeks to promote the resilience of refugees and improve their access to mental health care. For this purpose, Problem Management Plus (PM+), an evidence-based low-intensity psychological intervention delivered by trained non-specialist “helpers”, is being scaled-up in Switzerland.ObjectiveTo identify factors influencing the process of the large-scale implementation of PM + for refugees in Switzerland and to develop recommendations to guide the implementation process.Methods22 semi-structured interviews were conducted with key informants (Syrian refugees who previously participated in PM+, PM + helpers, health professionals working with refugees and decision-makers from the migration, integration, social, and health sectors). The data were analyzed using thematic analysis, combining an inductive and deductive approach.ResultsThe data revealed three major themes, which might have an impact for the longer-term implementation of PM + in Switzerland. First, preconditions for successful integration in the health system prior to scaling-up such as sustainable funding or the introduction of a stepped care approach. Second, the requirements for the PM + intervention supporting scale-up such as quality control during PM + delivery, PM + modality, time and setting when PM + is offered or the views on task sharing. Third, the perceived benefits of scaling-up PM + in Switzerland.ConclusionsOur results have shown that PM + must be scaled-up within a stepped care approach, including a functioning triage system and sustainable funding. Rather than selecting one modality or setting, it seemed preferable to offer a variety of formats and settings to achieve maximum reach and benefits. A successful scale-up of PM + in Switzerland might have various benefits. Communicating them to policy-makers and health providers, might enhance their acceptability of the intervention and their willingness to adopt PM + in regulatory structure and promote it.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12913-023-09491-8.