Professional learning communities (PLCs) are being recognized as effective in improving teacher collaboration and student achievement. Trust is critical in effectively implementing the PLC model, and the school principal is best positioned to influence school trust levels. Using five facets of trust, this research sought to clarify the impact of trust among PLC teachers on their team's collaborative practices. Findings suggested ways that members of successful PLCs built trust. Findings also suggested ways that principals influenced team members' trust. Successful and unsuccessful PLCs emphasized different facets in describing development of trust, the principal's role in building trust, and the role of trust in collaboration.