Despite growing evidence of positive student outcomes from course-based undergraduate research experiences (CUREs), little consideration has been given to employing graduate teaching assistants (GTAs) as CURE instructors. GTAs may be novice researchers and/or teachers and likely vary in their interest in teaching a CURE. Guided by expectancy-value theory, we explored how GTAs’ self-efficacy and values regarding teaching a CURE impact motivation and perceptions of their roles as CURE instructors. Using a multiple case study design, we interviewed nine GTAs who taught a network CURE at one research institution. Though most GTAs held a relatively high value for teaching a CURE for a range of reasons, some GTAs additionally perceived high costs associated with teaching the CURE. Through the interview data, we established three profiles to describe GTA perceptions of their role as CURE instructors: “Student Supporters,” “Research Mentors,” and “Content Deliverers.” Those implementing GTA-led CUREs should consider that GTAs likely have different perceptions of both their role in the classroom and the associated costs of teaching a CURE. The variability in GTA perceptions of CUREs implies that undergraduate students of different GTAs are unlikely to experience the CURE equivalently.