Studies have indicated that a sense of community may be shaped by the built environment and has potential mental wellbeing implications. However, few studies have explored this pathway empirically. Moreover, research has rarely differentiated the role of objective and perceived built environment. Based on a survey of 1,553 older adults undertaken between 2015 and 2017 in Hong Kong, we explored the distal mediation pathway from objective built environment to both mental health and subjective wellbeing through perceived built environment and sense of community, using multilevel structural equation modeling. The results showed that perceived built environment and sense of community can fully explain the residential density and subjective wellbeing relationship. The inverted U-shape relationship between street connectivity and mental health was identified. Park-based green space had a protective role for both mental health and subjective wellbeing and was explained by two mediators, but vegetation-based green space was negatively associated with subjective wellbeing. Land use mix had positive total effects on both mental health and subjective wellbeing and was partially mediated by perceived built environment and sense of community. Recreational services showed a protective effect on both mental health and subjective wellbeing, and both were partially mediated by two mediators. The negative direct effect of health services on subjective wellbeing offsets the positive indirect effect through two mediators. The study findings have implications for landscape and urban planning policy and can provide an empirical contribution to the theoretical foundation of aging in place.