Introduction: Two billion people are currently affected by complex humanitarian emergencies (CHEs) resulting from natural disasters and armed confl ict. Many have been displaced into crowded camps with poor access to water, sanitation, and health care. Humanitarian response is challenging under these circumstances, raising concern about the impact of COVID-19 on crisis-aff ected populations. Methods: This article examines CHEs in the Democratic Republic of Congo, Bangladesh, and Yemen, where protracted crises have displaced millions of people. Through use of a conceptual model, we examine barriers and facilitators to an effective COVID-19 response in these complex settings, and explore the future impact of the pandemic on crisis-affected populations. Results: Younger populations, who tend to have less severe COVID-19 disease, and existing response mechanisms, including educational health messaging, may facilitate the COVID-19 response in some CHEs. However, pre-existing chronic illnesses and malnutrition, coupled with poor access to health care and limited water/sanitation infrastructure, may increase COVID-19 infection rates and mortality. Exacerbated health care shortages, food insecurity, interrupted immunizations, increased insecurity, and worsened poverty may have a particularly severe impact. Discussion: A wide-reaching global response, incorporating the voices of marginalized populations, is needed to effectively and equitably respond to this global pandemic. Given the potential future deployment of Canadian troops to CHEs, an understanding of the COVID-19 response and pandemic implications in CHEs is critical for Canadian Armed Forces members. © 2020 Journal of Military, Veteran and Family Health. All rights reserved.