In this article we investigate how human and social capital contribute to individual productivity. We study three firms that complete all their tasks as projects. The employees in all firms initiate and organise their projects. We collected archival data from the firms on performance, human capital, tenure, gender and their project activities. Social network data are generated from interviews and a survey. We find that social capital is the most important factor to determine productivity. We found mixed effects from human capital; only in one firm did human capital have a noticeable effect on productivity; tenure has no effects on productivity.