Although Evidence-Based Instructional Practices (EBIP) generally improve students’ performance in STEM, traditional lecturing remains the most common instructional practice in postsecondary settings. This study examines an institutional change program that organized STEM faculty into communities of practice (CoPs) to facilitate the adoption and spread of EBIP in postsecondary classrooms. In this program, CoPs were mentored by faculty members who have a track record as advocates for high-quality teaching. In order for practices to spread, knowledge about those practices needs an avenue to spread. We hypothesized that CoP mentors provide these avenues by creating bridging ties between the disparate CoPs, thus spanning structural holes. To test the hypothesis, a sociometric survey was administered to document 100 faculty members’ social interactions concerning teaching. A Monte Carlo permutation test revealed that the mentors significantly increased the density, connectedness, and centralization of the institutional change program’s teaching social network more than any other random selection of faculty members. We also found that CoP mentors were the most likely individuals to connect otherwise unconnected CoP participants. These findings suggest that the CoP mentors played an important role in providing the bridges that can facilitate the spread of knowledge about teaching innovations across the network.