This study estimates the causal economic losses in South Korea’s travel industry attributable to government-imposed COVID-19 assembly bans using a synthetic difference-in-differences design, linking KISVALUE firm-level panel data on externally audited corporations (2010–2021) to granular policy records for the Seoul metropolitan area and constructing controls from passenger transportation and other contact-intensive industries with similar demand conditions. We find that assembly bans lowered operating profits by KRW 0.3132–0.3985 trillion in 2020 and KRW 0.3580–0.3815 trillion in 2021— equivalent to 3.6–4.6% and 4.2–4.4% of 2019 travel-industry revenue (KRW 8.627 trillion)—suggesting economically large and persistent losses and highlighting the value of incorporating industry heterogeneity in future public-health policy design.