Social frailty, along with physical and psychological frailties, is one of the components of frailty that has been reported to increase the incidence of adverse health outcomes. Although the prevalence of social frailty is relatively high, consensus on how to define and measure it is insufficient. In considering social frailty, living alone, interaction with neighbors, and social participation are important indicators, and interaction with neighbors and social participation, which are modifiable factors, are important countermeasures. The promotion of these social activities will contribute to extending healthy life expectancy—for example, by promoting physical activity. However, older people's physical and social activities have been severely constrained by the coronavirus pandemic since 2020. In the future, it will be necessary to fully understand the characteristics and significance of social frailty and develop appropriate countermeasures.