This study examines the ties of sixth-grade teachers to their interdisciplinary team colleagues and explores the dimensions of their efficacy beliefs for their own and their colleagues' teaching. Teachers (n = 238; 83% female, 88% White) from 26 middle schools completed surveys about the relational aspects of ties to team colleagues, the dimensions of their sense of efficacy for teaching, and their perceptions of team members' collective efficacy at fall, winter, and spring of one school year. Greater tie strength in fall predicted greater relational trust at winter and spring. Tie strength to teammates in fall predicted greater efficacy beliefs for classroom management and collective efficacy across the year, through greater relational trust midway through the year. The findings expand theorizing and reveal organizational processes that may be used to leverage teacher efficacy beliefs.