This study investigated changes in life expectancy due to the COVID-19 pandemic by analyzing the contributions of age, gender, and cause of death in 2019 and 2022. Korea’s simplified life table and cause-of-death statistics from 2019 to 2022 were used to assess mortality changes by age, gender, and cause of death during the pandemic. Joinpoint regression analysis was applied to detect trends, and the Arriaga decomposition method was used to quantify the contributions of age, gender, and cause of death to life expectancy changes. Joinpoint regression identified a slow increase in life expectancy in 2007 and a decline in 2020, coinciding with the COVID-19 pandemic. Life expectancy decreased markedly for men (-0.36 years per year, 95%CI: -0.68 to -0.03) and women (-0.45 years per year, 95%CI: -0.71 to -0.18). Age-specific contributions revealed declines across age groups, with the steepest reductions in the older population (80 years or older: -0.35 years for men; -0.52 years for women). Women (-0.68 years) contributed more to the decline in life expectancy than men (-0.41 years). COVID-19 ranked as the third leading cause of death in 2022, significantly contributing to the decline in life expectancy among the older population (aged 80 years or older: -0.306 years for men, -0.408 years for women). Women in Korea were more affected than men, reducing the gender gap in life expectancy by 0.3 years. Before the pandemic, non-communicable diseases such as malignant neoplasms, heart disease, and cerebrovascular disease dominated Korea’s top 10 causes of death. During the pandemic, however, COVID-19 rose to third place by 2022. Notably, intentional self-harm (suicide) contributed to an increase in life expectancy, suggesting shifts in the relative impact of various causes of death