Graduate teaching assistants (GTAs) play a significant role in higher education and in the education of undergraduate students. Previous research suggests that undergraduate students perceive GTAs differently than faculty instructors, but little has been done to explore the nature of those perceptions. This exploratory study uses self-determination theory to investigate how university students describe the effective teaching practices of GTAs and how those descriptions vary depending on GTA gender, GTA international status, and course domain. Findings suggest that the majority of undergraduates described GTAs' competence-supporting practices and that descriptions varied based on GTAs' international status and on course domain. Implications for GTA training are discussed.