OBJECTIVE: The COVID-19 pandemic led to an increase in mortality in most countries in 2020, deviating from prior decreasing trends. In Japan, however, mortality was suggested to decrease in 2020. This study investigated long-term mortality trends and cause-specific contributions, focusing on the period of the COVID-19 pandemic in Japan. DESIGN: We analysed Japanese age-standardised mortality rates (ASMRs) from 1995 to 2021 using vital statistics. MAIN OUTCOME MEASURES: The cause-specific annual ASMR changes were calculated in comparison with the previous year over the abovementioned period. RESULTS: There was a general downward trend in overall ASMR for both sexes until 2020 followed by a small increase in 2021. In men, the all-cause ASMR (per 100 000 persons) decreased from 1352.3 to 1328.8 in 2020 (-1.74% from 2019), and increased to 1356.3 in 2021 in men (+2.07% from 2020). In women, the all-cause ASMR decreased from 746.0 to 722.1 in 2020 (-3.20% from 2019), and increased to 737.9 (+2.19% from 2020) in 2021. ASMRs from malignant neoplasms, pneumonia, accidents and suicide (men only) continued to decrease during the COVID-19 pandemic while the trend of cardiovascular mortality increased in 2021. Analysis of ASMR changes revealed that COVID-19, senility, cardiovascular disease and 'other causes not classified as major causes' contributed to the all-cause mortality increase in 2021. CONCLUSIONS: In Japan, the decreasing trend in overall mortality continued in 2020 despite the COVID-19 pandemic. However, approximately 2% mortality increase was observed in 2021, which was attributable to COVID-19, senility, cardiovascular disease and 'other causes'. The year 2021 was a turning point of mortality trends in Japan, although continued monitoring is warranted.