International migrant workers (IMWs) may face insecure work and housing, limited access to healthcare and increased risk of psychological problems. Two scalable, evidence-based interventions to support individuals experiencing psychological distress are Doing What Matters in Times of Stress (DWM) and Problem Management Plus (PM+). This study aimed to explore IMWs’ problems, daily functioning and help-seeking behaviour, to inform cultural adaptation of the DWM/PM+ stepped-care intervention in the Netherlands. Following the Design, Implementation, Monitoring, and Evaluation (DIME) model, we conducted various qualitative interviews and a focus group discussion with IMWs (n = 30) and professionals (n = 18). Data were analysed thematically, and findings informed adaptations. Participants described problems related to work, housing, administration, finances, healthcare access and the COVID-19 pandemic. Daily routines focused on practical needs. Help-seeking was hindered by stigma, fear of job loss, low trust and reliance on informal or cross-border healthcare. Based on these results, the intervention was adapted to the needs of Polish IMWs in the Netherlands, regarding content and examples, which were tailored to their context; the intervention was offered remotely and collaboration with employers was avoided. These findings highlight the structural vulnerabilities of IMWs and demonstrate how qualitative insights can guide the cultural adaptation of a psychological intervention.