Mindset, or the implicit theories of intelligence, has attracted extensive attention in research and practice. However, it has predominately been measured using explicit, self-reflective survey items. Given the potential self-reporting bias and the nature of the construct, this study developed a novel Implicit Association Test (IAT) of growth mindset, alongside alternative measures such as forced-choice and scenario assessments, to investigate their relations with academic performance. We employed a two-step approach: Study 1 began with an initial sample of 200 university students, comprehensively examining the relations between the IAT, traditional self-reported mindset measures, alternative mindset measures, effort beliefs, and social desirability. Results showed that the IAT, unlike self-reported mindset measures, was not affected by social desirability. In Study 2, we extended our sample to a total sample size of 688 (Mean age = 22.3). This larger study found that the IAT growth mindset measure correlated weakly with traditional self-reported growth and fixed mindset measures (r = 0.14 and - 0.23, respectively) and demonstrated small but significant incremental validity over self-reported mindset in predicting academic achievement. In sum, our findings suggest that explicit measures of mindset may not fully capture people's implicit attitudes and beliefs about intelligence. Integrated measures of mindset might be warranted and helpful to address the recent debates on the effectiveness of growth mindset and achievement.