Drawing on a citywide survey of 39 urban neighborhoods and a qualitative case study of a neighborhood in Guangzhou, China, this research addresses how communal space, social capital, and neighborhood attachment (NA) jointly shape neighborhood participation (NP). Communal space is strongly and significantly associated with NP. Furthermore, we find that communal space is related to NP in two ways: promoting place-based social relations (the social-capital mechanism) and nurturing place attachment (the intrapsychic mechanism). These findings point to the significance of communal space as a civic focal point in community building and place making.