Because little work exists on the sense of belonging focusing on just Black undergraduate women in science, technology, engineering, and math (STEM), especially at highly selective predominantly white institutions (PWIs), this study takes a phenomenological approach to understand the lived experiences of Black undergraduate women in STEM by exploring how racial and gendered microaggressions influence how three African American women majoring in the sciences experience sense of belonging at PWIs. A phenomenological inductive analysis was used to compile the research findings, which indicated that racial and gender discrimination, isolation, marginalization, and alienation resulting from microaggressions occurred. Implications for inclusive practices are discussed.