This cross-sectional study examined associations of local social engagement with walking and sitting, and whether these associations were modified by local environmental attributes. Older residents (aged 65–84 years, n = 849), recruited from a regional city in Japan, reported walking frequency, sitting time, local social engagement, and local environmental attributes. Walk Score® was also used as an environmental measure. Analysis of data from 705 participants found that engaging in community activities was significantly associated with more frequent walking, but not with prolonged sitting. Interaction analyses between social engagement and environmental attributes did not show any significant interactions, suggesting that promoting local social engagement may increase walking frequency among older adults, regardless of local environmental characteristics. Community-level social initiatives that encourage older adults to participate in local meetings, events, and activities may be an effective physical activity promotion strategy among older adults.