Social capital generated by frequent, face-to-face interactions provides the foundation for collective action. Does this also hold for a community action in post-communist, Central European countries where modern NGOs are perceived to be ineffective? This article examines this question in the context of the cleanup of illegal dumpsites organized by a Slovenian NGO, Ecologists without Borders, in 2010. This community cleanup effort sought to produce local public goods such as improved aesthetics, sanitation, and ground water quality. Local participation levels (percentage of adults contributing to the cleanup effort) varied across 192 districts of Slovenia. Analyzing an original, micro-level dataset, this article finds that, all else equal, social capitals rooted in frequent face-to-face interactions (the common Catholic religion and membership in Hunters clubs) are associated with increased participation levels. However, social capital generated via common native language does not show statistical association with participation levels.