Since 2013, the Boko Haram insurgency in Nigeria has left almost 2 million people displaced and 10 million in need of life-saving services. While the humanitarian response has focused on provision of food, shelter, and physical health needs, mental health needs remain largely overlooked. This mixed-methods project explored the mental health and psychosocial (MHPS) burden, existing resources and coping mechanisms, and remaining needs among internally displaced persons (IDPs) and host communities in Borno State, Nigeria. Survey findings reveal a high burden of mental health needs: 60% of participants strongly endorsed at least one mental health symptom, and 75% endorsed functional impairment associated with mental health symptoms. Unexpectedly, we found that adult men had the highest rates of symptom burden, suggesting that typical approaches focusing on women and children would miss this vulnerable population. Qualitative findings (free lists, interviews, focus group discussions) reflect MHPS needs that could be addressed through solutions-focused approaches, although tailored interventions would be needed to support stigmatised and vulnerable groups such as drug users and rape victims. Finally, participants emphasised the breakdown of community and political leadership structures, as well as of economic and livelihood activities, suggesting that MHPS interventions should focus on restoring these key resources.