Student-instructor interactions have an influence on student achievement and perceptions of learning. In college and university settings, large introductory STEM courses are increasingly including Peer-Led Team Learning (PLTL), an evidence-based technique associated with improved student achievement, recruitment, and retention in STEM fields, especially for underserved populations. Within this technique, peer leaders hold a unique position in a student’s education. Peer leaders have relevant experience in that they have had recent success in the courses in which they facilitate student learning, yet, compared to student-faculty or student-teaching assistant relationships, there is minimal imbalance of authority or power. Students might find their peer leaders to be more relatable than faculty or graduate teaching assistants, and may even consider them to be role models. We explored students’ perceptions of peer leader relatability and role model status in relation to students’ achievement and their perceived learning gains in the context of an introductory biology course with an associated PLTL program. The final course grades and self-assessed learning gains of PLTL students who felt they related to their peer leader were compared to those who did not. We also compared final course grades and self-assessed learning gains between PLTL students who viewed their peer leader as a role model versus those who did not. Self-reported learning gains were significantly higher for students who relate to their peer leader, as well as for students who viewed their peer leaders as a role model. There is some support that this trend is stronger for STEM majors versus those who are not enrolled in a STEM program, though the interaction is not significant. Significant differences in overall course grade were only observed between students who reported that they related to their peer leader versus those who did not relate to their peer leader.