I introduce the construct of fragile and robust identities for the purpose of exploring the experiences that influenced the mathematical and racial identities of highachieving Black college students in mathematics and engineering. These students maintained high levels of academic achievement in these fields while enduring marginalization, stereotyping, and other forms of racialization. Their fragile mathematical identities were manifested in the way they were motivated to achieve in order to prove false the negative expectations of others. Their robust mathematical identities were characterized by an evolving sense of self-efficacy and discovery, a growing affinity and passion for mathematics, and a desire to be a mathematically inspiring role model. Extending the work on identity development, I recommend more nuanced interpretations of the interplay of human development, racialized experiences, and distinctly race-related risk and protective factors that complicate mathematical identity formation for Black college students in mathematics and engineering fields.