Neighborhood Open Spaces (NOS) such as public spaces around people's homes, parks and village greens, may support activity and socializing for older adults. These spaces might be especially important for older adults as they typically are less mobile and have smaller activity spaces and social networks than other age groups. The present exploratory sequential mixed methods study investigates the association between built environment features, social interaction, and walking within NOS, among older adults living in a low socio-economic neighborhood in Copenhagen. Interviews, the Community Park Audit Tool, and the System for Observing Play and Recreation in Communities (SOPARC) were used to capture quantitative and qualitative data on 353 older adults (59-90 years old) within 11 NOS. Walking was predicted by the condition and shade along paths, seating and landscaping. Social interaction was negatively associated with walking, suggesting that older adults tend to sit down when engaging in social activities. Interviews highlighted the importance of social interaction within NOS. Future designs of NOS should acknowledge the importance of social meeting places, but at the same time provide walkable spaces for older adults to promote healthy aging.