Using plasma biomarkers and state-of-the-art MR techniques to measure the CP volume and its microstructural integrity, the current study provides the first evidence that elevated plasma markers of Alzheimer’s disease (AD) pathology (Aβ42/Aβ40 and pTau181), neuronal injury (NfL), and neuroinflammation (GFAP) are associated with differences in the CP’s macro- and micro-structure in cognitively normal adults. Here, GFAP is linked to early-onset autosomal dominant Alzheimer disease.