Canada is facing a teacher shortage, a crisis exacerbated by the exodus of 30% of new teachers from the profession. In response, educational stakeholders are anxious to find ways to recruit and, more importantly, retain new teachers. This chapter addresses the impact of teacher mentoring on new teacher efficacy. Research has long shown the link between a strong sense of teacher efficacy and teacher effectiveness. Through a comprehensive literature review, the study examines the theory behind teacher efficacy, how teacher mentoring supports the development of teacher self-efficacy and the connections between new teacher participation in mentoring programs and their commitment to remaining in the profession. Beginning with the Social Learning Theory of Bandura, the study looks at how teacher efficacy develops and how it affects the professional behavior and perspectives of new teachers. Next, I examine the positive influence of teacher mentoring on new teachers’ professional development and efficacy. Finally, I review studies which show that early teacher mentoring can increase and accelerate the development of new teacher efficacy and discuss the impact of this mentoring on new teacher retention.