To provide meaningful, high-quality learning experiences for students with diverse academic backgrounds, a critical consideration for mathematics educators is student engagement. The approach of team-based learning has allowed for an increase in student-centered class time and demonstrated positive results in tertiary education across multiple disciplines. However, this approach has been primarily used at the tertiary level and has not yet been empirically examined in middle school mathematics. Our mixed methods study of team-based learning in an eighth-grade mathematics class examined the influence of students' team type (i.e., mixed sex, same-sex) and perceptions of team members' contributions on students' engagement in their mathematics class. Results of the study provide evidence for the positive effect of team-based learning on engagement as well as support for the critical role of peer interactions. Our findings provide implications for implementing team-based learning in secondary mathematics education for educators and researchers.