The dilemma of weak participation and non-participation of rural communities is a universal topic of global development. The rural public space is an important field for local residents to interact, communicate, and engage with each other, and is an important place for the sustainable development of rural areas. However, previous studies have neglected to understand the intrinsic connection between rural public space and community participation from the perspective of community communication ecology. Based on the concept of age-friendly communities, this study’s fieldwork in rural Shanghai, China, using the methodology of grounded theory, found that physical, social, and psychological factors all have an impact on community engagement among rural residents. Specifically, environmental quality, facility support, community networks, social participation, call to action, place attachment, spatial perception, and self-transformation are identified as the core elements that significantly influence community engagement among rural residents. This study further reveals that the multiple factors influencing community engagement among rural residents are complex and interdependent rather than operating independently. Spatial support, communicative triggers, and symbolic identification, respectively, operate at the technological level (physical–social factors), social level (social–psychological factors), and discursive level (psychological–physical factors) to promote community engagement among older adults in Chinese rural areas. Through this research, we hope to further the realization of rural civic engagement and the sustainability of local communities and to provide scholarly insights into the promotion of more equitable community life.