Self-efficacy is a perceived judgment that one has the ability to execute a course of action that brings about a desired result. Principal self-efficacy describes a set of beliefs that enable a principal to enact policies and procedures that promote the effectiveness of a school. Principal self-efficacy beliefs are also important because they guide the leader's actions and behaviors that affect expectations for students as well as teachers' motivation and school improvement processes. In this qualitative case study, we sought to understand teachers' perceptions of how the self-efficacy beliefs and actions of the principal contributed to the school's collective efficacy. The study featured a single embedded case design highlighting one high poverty rural middle school with very high levels of achievement. While collective efficacy was developed through fidelity to instructional initiatives and relationship building among staff, the efficacy beliefs and actions of the principal influenced the school's collective efficacy by creating a steadfast instructional focus, developing teacher leaders, and leading by example.