We analyse the firm-level labour productivity growth returns of social capital ―defined as a synthetic measure of ‘generalised trust’, ‘active participation’, and ‘social norms’― using a large sample of manufacturing firms in France, Germany, Italy, Portugal, and Spain. We find that firms’ labour productivity growth is higher in areas with a better social capital endowment. The positive returns of social capital are, nevertheless, unevenly distributed across firms, with smaller, less productive, less capital-endowed, and low-tech firms benefitting the most from operating in strong social capital ecosystems.