Summary Background Adverse childhood experiences (ACEs) are associated with increased health risks across the life course. We aimed to estimate the annual health and financial burden of ACEs for 28 European countries. Methods In this systematic review and meta-analysis, we searched MEDLINE, CINAHL, PsycINFO, Applied Social Sciences Index and Abstracts, Criminal Justice Databases, and Education Resources Information Center for quantitative studies (published Jan 1, 1990, to Sept 8, 2020) that reported prevalence of ACEs and risks of health outcomes associated with ACEs. Pooled relative risks were calculated for associations between ACEs and harmful alcohol use, smoking, illicit drug use, high body-mass index, depression, anxiety, interpersonal violence, cancer, type 2 diabetes, cardiovascular disease, stroke, and respiratory disease. Country-level ACE prevalence was calculated using available data. Country-level population attributable fractions (PAFs) due to ACEs were generated and applied to 2019 estimates of disability-adjusted life-years. Financial costs (US $ in 2019) were estimated using an adapted human capital approach. Findings In most countries, interpersonal violence had the largest PAFs due to ACEs (range 14· 7–53· 5%), followed by harmful alcohol use (15· 7–45· 0%), illicit drug use (15· 2–44· 9%), and anxiety (13· 9%–44· 8%). Harmful alcohol use, smoking, and cancer had the highest ACE-attributable costs in many countries. Total ACE-attributable costs ranged from $0· 1 billion (Montenegro) to $129· 4 billion (Germany) and were equivalent to between 1· 1%(Sweden and Turkey) and 6· 0%(Ukraine) of nations' gross domestic products. Interpretation Availability of ACE data varies widely between countries and country-level estimates cannot be directly compared. However, findings suggest ACEs are associated with major health and financial costs across European countries. The cost of not investing to prevent ACEs must be recognised, particularly as countries look to recover from the COVID-19 pandemic, which interrupted services and education, and potentially increased risk factors for ACEs. Funding WHO Regional Office for Europe.