To transition introductory college science courses from large, passive lectures to more student-centered learning environments, additional instructional support is needed. Peer learning assistants (PLAs) can support that transformation by engaging students in interactive discourse and collaborative learning during class activities. PLAs are trained to use several pedagogical strategies while interacting with students to facilitate learning. In this study, we investigated the impact of PLAs on student learning in an introductory biology course by comparing student performance on exam questions that aligned with two types of class activities: clicker questions and open-response group activities. We also conducted a survey about student perceptions of PLAs that focused on three themes: PLA practices, student trust in PLAs, and student value of PLAs. We found that students performed significantly better on exam questions that aligned with open-response group activities rather than clicker questions. Students found their interactions with PLAs helpful for learning and valued having PLAs in class. Furthermore, students agreed that PLAs used a variety of strategies to assist their learning. We offer several implications for PLA pedagogy training and considerations for classroom activities in which PLAs may provide the most benefit to student learning.