ObjectivesThe data presented in this note were collected during a multi-year project conducted in the context of large-enrollment introductory biology course at a large private R-1 research institution in the Northeastern United States. The project aimed to examine the impact of Peer-Led Team Learning (PLTL) on the recruitment and retention of marginalized groups in Science, Technology, Engineering, and Mathematics (STEM) majors. While several results from the project have been published, additional data of interest have yet to be reported. This data note reports on additional associations between PLTL participation and improved outcomes for students from groups that have historically been excluded in STEM. Additional data reported herein were collected to determine if students in the course experienced imposter phenomenon, and whether PLTL may be associated with reduced levels of imposter feelings.Data descriptionThe data in this note includes academic information such as final course grades and academic level; socio-demographic information such as gender identity, minority status, and first-generation status; and information on student recruitment, retention, imposter feelings, and participation in Peer-Led Team Learning (PLTL). These data might be useful and of value to education researchers and undergraduate STEM instructors who are interested in improving equity in STEM education.