Four individual studies investigated the effect of mentor teacher leadership characteristics on student intern efficacious beliefs. The leadership characteristics embodied four separate leadership related theories: transformational leadership, authentic leadership, leader-member exchange theory, and servant leadership. Teacher efficacy was based upon Tschannen-Moran and Hoy's Teacher Sense of Efficacy Scale which included three sub-scales: student engagement, instructional strategies and classroom management. All studies took place during the Spring semester of four different years (2009, 2012, 2013, and 2014) in one Mid-Atlantic University's pre-service teacher practicum experience within the framework of 33-34 Professional Development Schools. The sample included 634 student teacher interns who were paired with 634 teacher mentors. The compounding and unique results of each of the studies offers insightful lessons to mentor teachers, PDS schools, and educator preparation programs.