The COVID-19 pandemic has highlighted the importance of indoor environmental management in facilities vulnerable to infection, such as long-term care facilities, where residents remain indoors for extended periods. In light of this, this study investigated the architectural characteristics and ventilation conditions of long-term care facilities in South Korea using a nationwide survey. An online survey targeting 12,425 facilities was conducted in April 2022, and valid responses from 5,550 facilities were analyzed. The survey examined building layouts, ventilation methods, mechanical ventilation systems, air purifier use, and ventilation operation and maintenance. The results showed that numerous facilities had architectural configurations unfavorable for natural ventilation, including a high proportion of double-loaded corridor layouts. Mechanical ventilation systems were installed in only 41.4% of facilities, whereas air purifiers were present in 72.3%, indicating a reliance on air cleaning rather than outdoor air ventilation. Although ventilation managers and regular inspections were commonly reported, formal operation and maintenance manuals were less prevalent. These findings indicate structural and system-level limitations in achieving stable ventilation performance in long-term care facilities. Additionally, they provide baseline data to support improvements in ventilation strategies and policies for infection-vulnerable facilities.