This study detects statistically significant and substantively large stereotype threat effects that would remain hidden if Black identification were measured only explicitly. Three hundred and fifty-one students at Historically Black Colleges and Universities (HBCUs) were tested on an implicit Black identification measure in an online survey, and stereotype threat was manipulated beforehand by randomly presenting one of three introductory screens: an all-White research team (high-threat condition), an all-Black research team (low-threat condition), or no team picture (control condition). The implicit Black identification measure predicted pro-Black political opinions (regarding affirmative action and government aid to Blacks, slavery reparations, and the Racial Resentment Scale), high performance on a political knowledge test, and high self-reported political participation. However, under the high-threat condition, Black students with the highest implicit Black identification scores answered 25% fewer political knowledge questions correctly, and reported 25% fewer acts of political participation, compared with students operating under the low-threat conditions. (C) 2017 Elsevier Inc. All rights reserved.