Social identity and acculturation research mostly documents benefits of dual identity for immigrant minorities’ adaptation. Drawing on stereotype threat research, we argue that dual identity can be (1) beneficial in low-threat contexts and (2) costly in high-threat contexts. Two field experiments in schools induced stereotype threat by randomly assigning minority students (Study 1: N = 174, Study 2: N = 735) to stereotype threat (making ethnicity salient) vs. control conditions before taking a test. We assessed dual identity as dual commitments to (combined) minority and majority cultures. In support of the predicted benefits of dual identity in low-threat contexts, dual identifiers outperformed and had higher self-esteem than did otherwise-identified students in the control condition, while the advantage of dual identity disappeared in the threat condition (Study 1). In support of the predicted costs of a dual identity in high-threat contexts, dual identifiers reported more anxiety (Study 1) and performed worse (Study 2) in the threat condition compared to the control condition. These experimental findings suggest that dual identities may either help or hinder minority performance depending on stereotype threat in academic contexts.