Burnout is a global work-related phenomenon. Intensive care unit (ICU) nurses are at risk of burnout and the COVID-19 pandemic may increase this risk. The objectives of this study were to assess the prevalence of burnout risk and identify risk factors among ICU nurses during the COVID-19 pandemic. Web-based survey performed during the first wave of the COVID-19 pandemic in French speaking Belgium. Risk of burnout was assessed with the Maslach Burnout Inventory scale. A total of 1135 ICU nurses responded to the questionnaire. The overall prevalence of burnout risk was 68%. A total of 29% of ICU nurses were at risk of depersonalisation (DP), 31% of reduced personal accomplishment (PA), and 38% of emotional exhaustion (EE). A 1:3 nurse-to-patient ratio increased the risk of EE (ORÂ =Â 1.77, 95% CI: 1.07-2.95) and DP (ORÂ =Â 1.38, 95% CI: 1.09-2.40). Those who reported having a higher perceived workload during the COVID-19 pandemic were at higher risk for all dimensions of burnout. Shortage of personal protective equipment increased the risk of EE (ORÂ =Â 1.78, 95% CI: 1.35-3.34) and nurses who reported having symptoms of COVID-19 without being tested were at higher risk of EE (ORÂ =Â 1.40, 95% CI: 1.68-1.87). Two-thirds of ICU nurses were at risk of burnout and this risk was associated with their working conditions during the first wave of the COVID-19 pandemic. We recommend monitoring the risk of burnout and implementing interventions to prevent and manage it, taking into account the factors identified in this study.