Abstract: COVID-19 has presented a substantial burden on students and healthcare staff. This mixed-method, descriptive and correlational study aimed to: 1) describe academic; and 2) professional burnout levels; 3) their associations with working in COVID-19-related care; and 4) with perceived COVID-19 impact on studies and internships among medical students and residents. We hypothesized burnout levels to be high; those involved in COVID-19 care to experience higher impact of COVID-19 on studies and work, and to experience higher levels of academic and professional burnout than those not involved in COVID-19 care; academic and professional burnout to be higher when perceived burden due to COVID-19 was higher. During first lockdown in Belgium, a mixed-method cross-sectional survey assessed academic burnout (MBI-SS) and professional burnout in relation to internships and residency (MBI-HSS). Correlations and t-tests tested associations of burnout with involvement in COVID-19-related care and perceived impact of COVID-19 on studies and work (SPSS). Participants provided open-ended comments which were thematically analysed (NVivo). In total, 194 medical students and residents participated (79.5% female, M age = 24.9 ± 2.5). Emotional exhaustion and depersonalisation were high in professional burnout, but moderate in academic burnout. Those involved in COVID-19 related care perceived a higher impact of COVID-19 on their studies and internship/residency and have higher professional burnout, but do not show a higher academic burnout. Those who have a higher perceived impact of COVID-19 on their studies scored higher on academic burnout. Participants mentioned an increased workload (e.g., having to be constantly available and constantly adapt), distress (e.g., uncertainty, fatigue, fear for impact on significant others), fewer learning opportunities (e.g., cancelled internships, changing learning methods), lack of relatedness with patients and supervisors (e.g., lack of respect and understanding from supervisors, ...