The purpose of this study was to examine the mediating effect of physical activity literacy in the effect of autonomy support on social isolation, loneliness, and perceived vitality. A self-reported survey was conducted on 300 adults (aged 20-65 years). Background variables, autonomy support, physical activity literacy, social isolation, loneliness, and vitality were measured using the questionnaire. Frequency analysis, confirmatory factor analysis, descriptive statistical analysis, and mediating analysis were conducted. It was found that autonomy support has a direct effect on social isolation, loneliness, and vitality. In addition, physical literacy showed mediating effects in the relationship between autonomy support and social isolation, loneliness, and vitality. Further research will be warranted to find a way to improve physical activity literacy among adults in order to reduce social isolation and loneliness and increase vitality.