Supplemental Instruction (SI) is an academic success program with a proven track record that was developed in the early 1970s to improve student academic performance in traditionally difficult courses (Arendale, 2000; Bonsangue et al., 2013; Bowles, McCoy, & Bates, 2008; Rabitory, Hoffman, & Person, 2015; Widmar, 1994). In over 40 years of program implementation, SI has been almost exclusively studied from the perspective of benefits to the Institutions of Higher Education (IHE) and the students receiving the instruction. Notably less research about SI has been conducted from the SI leader's point of view or included descriptions of their experiences in relation to changes in perception or critical self-reflection (A. W. Astin, 1985; Cress, Astin, Zimmerman-Oster, & Burkhardt, 2001). Using Mezirow’s (1991) transformative learning theory in combination with Nohl’s (2014) practice-based model as the theoretical structure, I conducted an interpretive qualitative study to investigate SI leaders' experiences. I interviewed former SI leaders who have held the position for at least 2 semesters in one of two institutions in different countries. The experience of being an SI leader shaped participants’ whole college experience, their post-graduate education, and professional careers. It also changed their perspectives about themselves, their career choices, and teaching and learning. Implications for policy and practice include teaching and learning connections, educating future teachers, structure and support for peer leaders, recruiting program leaders and participants, broadening student success, applied learning opportunities, and expanding the SI program. Implications for Mezirow's (1978) transformative learning theory in combination with Nohl's (2014) practice-based model include: the theories coexist and interact, context influences learning, stages may be skipped or experienced out of order, stages have nuances, and perspective transformation takes time.