Intellectual humility is increasingly recognized as a cognitive virtue that helps foster truth-seeking and compromise, and mitigating polarization. Yet the current body of evidence grapples with a striking contradiction: The prevailing theoretical account suggests that intellectual humility hinges on metacognitive ability—the capacity to introspect on one's own performance which manifests in assigning due confidence to the varying accuracy of one's performance. However, empirical research testing this metacognitive ability account of intellectual humility has yielded inconsistent results. Here, we introduce a cognitive science approach informed by Signal Detection Theory, allowing for a more nuanced separation of metacognitive ability from correlated but distinct concepts (i.e., confidence and task performance). We conduct a national survey study among a national US sample (N = 999) involving the interpretation of one of the most heavily contested domains—climate change—lending itself for an investigation into how intellectual humility relates to cognitive processes in domains where it is most needed. To gauge participants' ability to distinguish true from false interpretations of evidence (i.e., task performance), we presented them with four summaries of fictitious studies on renewable energy, followed by 2-alternative forced choice questions that assessed their accuracy and confidence in their responses. Results showed that firstly, more intellectually humble citizens performed better at discerning correct from incorrect interpretations of the presented evidence. Secondly, more intellectually humble citizens exhibited a heightened capacity to adjust their confidence levels to the varying accuracy of their evidence interpretations–indicating higher metacognitive ability—and this association was robust to accounting for their superior task performance, and other preregistered covariates. And thirdly, in contrast to intuitive notions, more intellectually humble citizens did not exhibit lower metacognitive bias, the inclination to report lower (vs. higher) confidence in general. By highlighting the role of metacognitive ability in intellectual humility, the current study delivers empirical evidence for the ancient notion that epistemic virtues may involve metacognitive ability.