The purpose of this research is to explore the relationship between age-friendly environment, social support, sense of community, and loneliness of Korean adults aged 45 and above. A total of 590 participants from a cross-sectional and secondary data from an age integration survey conducted in 2018 was used for analysis. Structural equation modelling and bootstrapping method were applied to examine the mediating role of social support and sense of community on the relationship between age-friendly environment and loneliness. Age-friendly environment was positively associated with social support () and sense of community (). Social support was negatively associated with loneliness (). Full mediation effect of social support was observed in the pathway from age-friendly environment to loneliness (95% CI: -0.135 to -0.036). Social support was fundamental in lowering loneliness in an age-friendly environment. There was no significant association linking age-friendly environment, sense of community, and loneliness. The results support the adoption of AFE to protect people at risk of loneliness with social support mediating this relationship.