Introduction: Long COVID (LC) is a medical condition first described and documented through anecdotes on social media by patients prior to being recognised by WHO as a disease. Although >50 prolonged symptoms of LC have been described, it remains a diagnostic challenge for military providers and therefore threatens operational readiness. Methods: On 9 September 2021, an online survey was emailed to 2192 Belgian Defence personnel who had previously tested PCR positive for SARS-CoV-2 between 17 August 2020 and 31 May 2021. A total of 718 validated responses were received. Descriptive analyses determined the prevalence of LC and 10 most common symptoms and their duration following infection. In the explanatory analyses, risk factors related to LC were identified. To establish the health-related impact of LC on quality of life (HRQoL), we used the results from the EuroQol 5 Dimension 5 Level questionnaire. Results: The most frequent symptoms that were reported for >3 months were fatigue, lack of energy and breathing difficulties. 47.35% of the respondents reported at least one persistent symptom, while 21.87% reported more than 3 symptoms lasting for at least 3 months after the initial COVID-19 infection. Most patients with LC suffered from symptoms of a neuropsychiatric nature (71.76%). LC was significantly associated with obesity; pre-existing respiratory disease and blood or immune disorders. Physical activity of >3 hours per week halved the risk of LC. The total QoL is reduced in patients with LC. Considering the five dimensions of the questionnaire, only the self-care dimension was not influenced by the presence of LC. Conclusions: Almost half of Belgian Defence personnel developed LC after a confirmed COVID-19 infection, similar to numbers found in the Belgian population. Patients with LC would likely benefit from a multidisciplinary rehabilitation approach that addresses shortness of breath, fatigue and mood disturbance. © Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and ...