We investigated two aspects of metacognition and their relationship with cortical thickness and Alzheimer's Disease (AD) biomarkers, amyloid and tau, in cognitively healthy older adults (N=151). The two metacognition measures were self-appraisal rating of task performance and the difference between self-appraisal rating and actual task performance (appraisal discrepancy). All participants underwent neuropsychological testing and 1.5T structural MRI. A subset (N=66) received amyloid-PET with

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... ] PiB and tau-PET with [18F] Flortaucipir. We found that worse performers had lower self-appraisal ratings, but still overestimated their performance, consistent with the Dunning-Kruger effect. Self-appraisal rating and appraisal discrepancy revealed distinct relationships with cortical thickness and AD pathology. Greater appraisal discrepancy, indicating overestimation, was related to thinning of inferior-lateral temporal, fusiform, and rostral anterior cingulate cortices. Lower self-appraisal was associated with higher entorhinal and inferior temporal tau. These results suggest that overestimation could implicate structural atrophy beyond AD pathology, while lower self-appraisal could indicate early behavioral alteration due to AD pathology, supporting the notion of subjective cognitive decline prior to objective deficits.