Black, Latine, and Indigenous students continue to face inequities in high school Science, Technology, Engineering, and Mathematics (STEM) outcomes in the United States (US). Racial disparities between teachers and students contribute to this issue, as teachers of color represent less than thirty percent of public-school educators, while most US youth are of color. Although prior research has emphasized the importance of racial/ethnic matching between teachers and students, limited knowledge exists about how matching can assist high school students of color in STEM high school outcomes (e.g., STEM course enrollment, math/science GPA). Additionally, previous research has traditionally focused on Black and White teachers and students, overlooking diverse teacher-student pairings (e.g., Black teacher with Latine students). Therefore, my two-study dissertation explored the mechanisms by which teacher-student racial/ethnic matching influences STEM outcomes for high school students of color, including diverse groupings of specific teacher-student pairs. Study 1 investigated the mechanisms by which racial/ethnic teacher-student match is associated with high school students of color's math and science GPA, via a structural equation model using data from the High School Longitudinal Study of 2009. Results revealed a nonsignificant or negative association between teacher-student racial/ethnic matches and student GPA, as well as teacher-led factors and student engagement. However, student engagement and teacher-led factors were significantly associated with student GPA, independent of teacher-student racial/ethnic matches. Study 2 continued this investigation and analyzed interview data of high school math and science teachers of color to explore how they perceive and work with students of color. Participants spoke to employing an intersectional approach when engaging and teaching their students, leveraging not only their racial/ethnic identity but also other identities such as language, gender, immigration status, and socioeconomic class. Overall, results emphasize the importance of nuance, suggesting that improving STEM outcomes for students of color requires consideration of multiple factors beyond race, such as enhancing the school environment, improving teacher practices and dispositions, and connecting with students of color through shared identities in addition to race/ethnicity. By recognizing this complexity, policies and practices can best support students of color and ultimately help reduce the racial underrepresentation in STEM. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]