BackgroundConsidering the heterogenous evidence, a systematic review of the change in anxiety in European children and adolescents associated with the COVID-19 pandemic is lacking. We therefore assessed the change compared with pre-pandemic baselines stratified by gender and age as well as evaluated the impact of country-specific restriction policies.MethodsA registration on the ‘International Prospective Register of Systematic Reviews’ (PROSPERO) occurred and an a priori protocol was published. We searched six databases (PubMed, Embase, PsycINFO, Cochrane Central Register of Controlled Trials, Web of Science, WHO COVID-19) using a peer-reviewed search string with citation tracking and grey literature screening. Primary outcomes were: (1) general anxiety symptoms; and (2) clinically relevant anxiety rates. We used the Oxford COVID-19 Stringency Index as an indicator of pandemic-related restrictions. Screening of title/abstract and full text as well as assessing risk of bias (using the ‘Risk of Bias in Non-randomized Studies of Exposure’ [ROBINS-E]) and certainty of evidence (using the ‘Grading of Recommendations Assessment, Development and Evaluation’ [GRADE]) was done in duplicate. We pooled data using a random effects model. Reporting is in accordance with the Preferred Reporting Items for Systematic review and Meta-Analysis (PRISMA) statement.ResultsOf 7,422 non-duplicate records, 18 studies with data from 752,532 pre-pandemic and 763,582 pandemic participants met full inclusion criteria. For general anxiety symptoms the total change effect estimate yielded a standardised mean difference (SMD) of 0.34 (95% confidence interval [CI], 0.17–0.51) and for clinically relevant anxiety rates we observed an odds ratio of 1.08 (95%-CI, 0.98–1.19). Increase in general anxiety symptoms was highest in the 11–15 years age group. Effect estimates were higher when pandemic-related restrictions were more stringent (Oxford Stringency Index > 60: SMD, 0.52 [95%-CI, 0.30–0.73]) and when school closures (School Closure Index ≥ 2: SMD, 0.44 [95%-CI, 0.23–0.65]) occurred.ConclusionGeneral anxiety symptoms among children and adolescents in Europe increased in a pre/during comparison of the COVID-19 pandemic; particularly for males aged 11–15 years. In periods of stringent pandemic-related restrictions and/or school closures a considerable increase in general anxiety symptoms could be documented.PROSPERO registration: CRD42022303714.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13034-023-00612-z.