Sharing knowledge among team members is critical to accomplishing innovation. However, there are motivation and communication barriers to sharing knowledge in teams. In this study of 219 work teams, two mechanisms that have potential for encouraging knowledge sharing (social capital and extrinsic incentives) are examined as they relate to tacit knowledge sharing, explicit knowledge sharing, and team innovation. Tacit knowledge sharing mediated the relationships between cognitive social capital and team innovation as well as between explicit knowledge sharing and team innovation. Explicit knowledge sharing mediated the relationship between relational social capital and team innovation, while both forms of knowledge sharing mediated the relationship between extrinsic incentives for knowledge sharing and team innovation.