Recent reform efforts in postsecondary science teaching have called for shifts in instructional methods to include more evidence-based instructional practices. However, a myriad of factors play a role in whether an instructor adopts these more student-centered methods. One such factor is teaching perspective. In this study, we explored the teaching perspectives of both graduate and undergraduate teaching assistants (TAs), as well as shifts in their perspectives after participation in an active-learning professional development course. Findings from this study suggest that while undergraduate TAs hold more nurturing perspectives of teaching, graduate TAs hold more apprenticeship perspectives; both groups, however, can experience perspective change through professional development and teaching experience. These findings have implications for professional developers and those who work closely with TAs.