OBJECTIVES: COVID-19 has had a profound impact on global mortality and morbidity, yet only a fraction of deaths was confirmed and reported. We estimated all-cause excess mortality from 1 January 2020 to 31 December 2022 in the Federation of Bosnia and Herzegovina (FBiH) to assess the true magnitude of the pandemic. METHODS: Data for this analysis was sourced from the FBiH mortality register and supplemented with population statistics and official COVID-19 death counts (i.e., cases where COVID-19 was registered as the cause of death). Using a Poisson model, all-cause excess number of deaths and rates per 100,000 person-years, adjusted for registration delays and stratified by age and gender, were calculated. RESULTS: FBiH experienced three periods of excess all-cause mortality throughout the first 3 years of the pandemic, with a total of 12,000 excess deaths, highest among adults 45-74 years and males. No excess mortality was observed in children <
15 years. CONCLUSIONS: The true mortality impact of COVID-19 in FBiH was substantially higher than the reported deaths, including among younger adults. Strengthening civil registration and vital statistics, including establishment of all-cause mortality surveillance, is essential for improved monitoring of future pandemics and other important public health events. A detailed review of the direct and indirect effects of COVID-19 on mortality should be conducted to identify areas that require more resources, improve health provision and inform mitigation efforts in future pandemics to save lives.