Research suggests there are potential benefits to students when taught by instructors who share the same gender and/or race/ethnicity. While underrepresented students have shown increased persistence and academic performance when they were taught by gender- and/or race/ethnicity-congruent faculty, there is little research that has explored the influence of matching for graduate student teaching assistants (GTAs). Given that science, technology, engineering, and mathematics (STEM) GTAs spend a significant amount of time with undergraduates, measurable impacts on student outcomes have the potential to contribute to the success of undergraduates who have been underrepresented in STEM fields. This study evaluated the effects on academic performance of GTA (n = 50) matching for first-year students (n = 976) in an introductory biology lab course at a Hispanic-serving institution. There was no significant difference in academic performance for students who matched with the gender, race/ethnicity, income, and first-generation status of their GTAs. Results were consistent across multiple cohorts of students, after including statistical controls for prior academic performance and other demographic characteristics and accounting for the nested structure of the data. These results suggest there is a need of supporting GTAs to develop more effective teaching practices and to consider effects of GTA matching on other outcomes.