OBJECTIVES: To determine the impact of the first COVID-19 surge (March through June 2020) on mental well-being and associated risk factors among intensive care unit nurses. RESEARCH METHODOLOGY: In September 2020, a nationwide cross-sectional survey study among Dutch intensive care nurses was carried out to measure prevalence rates of symptoms of anxiety, depression, posttraumatic stress disorder, and need for recovery (NFR), objectified by the HADS-A, HADS-D, IES-6 and NFR questionnaires, respectively. Associated risk factors were determined using multivariate logistic regression analyses. RESULTS: Symptoms of anxiety, depression, and post traumatic stress disorder were reported by 27.0%, 18.6% and 22.2% of the 726 respondents, respectively. The NFR was positive, meaning not being recovered from work, in 41.7%. Working in an academic hospital, being afraid of infecting relatives and experiencing insufficient numbers of colleagues were associated with more mental symptoms, while having been on holiday was associated with reduced depression symptoms and need for recovery. CONCLUSION: The first COVID-19 surge had a high impact on the mental well-being of intensive care nurses, increasing the risk for drop out and jeopardising the continuity of care. Effort should be made to optimize working conditions and decrease workload to guarantee care in the next months of the COVID-19 pandemic.