ObjectiveThe COVID-19 pandemic has had a significant impact on the burnout and mental health of medical staff. This meta-analysis aims to provide additional (and updated) evidence related to burnout and mental health problems among medical staff using a broader data pool.DesignSystematic review and meta-analysis.Data sourcesPubMed, Embase, Cochrane Library, CNKI, Wanfang data and three preprint databases (SSRN, bioRxiv and medRxiv) were searched from 1 January 2020 to 17 May 2021.Eligibility criteriaWe included observational studies investigating the prevalence of burnout and mental health problems among medical staff during the COVID-19 pandemic, including cross-sectional study, cohort study and case–control study.Data extraction and synthesisTwo independent reviewers used a self-designed form to extract the primary data. The Joanna Briggs Institute quality appraisal tool was used to assess the quality of selected studies. Heterogeneity among studies was assessed by I2statistic. A random-effects model was used to pool the prevalence. Subgroup analysis was performed to explore between-group differences.Results250 studies were included, with a sample of 292 230 participants from 46 countries. The pooled prevalence of burnout, anxiety, depression, insomnia, stress, post-traumatic stress disorder symptoms and somatic symptoms was 43.6% (95% CI 36.3% to 51.2%), 37.1% (95% CI 34.7% to 39.7%), 37.6% (95% CI 35.0% to 40.4%), 43.7% (95% CI 39.1% to 48.5%), 41.3% (95% CI 35.1% to 47.9%), 30.6% (95% CI 23.6% to 38.5%) and 25.0% (95% CI 16.7% to 35.6%), respectively. Subgroup analysis showed a higher prevalence of anxiety, depression and insomnia in frontline workers than in non-frontline workers, and a higher prevalence of anxiety in females than males. Mild cases accounted for the most significant proportion of the outcomes except for stress.ConclusionsThis study highlights that identifying the risks of burnout and mental health problems and adopting preventive interventions are priorities for policymakers and medical staff to avoid long-term occupational, health and social impacts.PROSPERO registration numberCRD42021254425.