Aid relief workers active in complex humanitarian emergencies often develop mental health issues, due to the complex context of these settings and several workplace stressors. In order to cope with these problems, aid relief workers rely on organizational preparation and support, and social support. However, there is a gap between the needs for and availability of preparation and support, which has negative effects on their mental health. This qualitative study provides a phenomenological review of the experiences of aid relief workers active in these complex humanitarian emergencies, with regard to mental health issues, levels of preparation, organizational support and social support. For this study, interviews with five aid relief workers in different fields were conducted to research the effects of working in complex humanitarian emergencies on their mental health, and how preparation and support, or the lack thereof, influences their psychological resilience. The results show that organizational preparation and support, and social support have a positive impact on the psychological resilience of aid relief workers. However, the availability of and access to adequate preparation and support often lacks, which has negative consequences for their mental health. Therefore, this study provides recommendations to humanitarian NGO’s to improve their mental health support, and explores how the psychological resilience of aid relief workers in complex humanitarian emergencies can be improved.