Plasma GFAP was significantly associated with β‐amyloid burden (β = 0.011, 95% CI = 0.0011–0.02, and P = 0.030) with large effect size (η2G = 0.3; 95% CI = 0.12–1.0); however, GFAP was not associated with gliosis (P = 0.35) or tau (P = 0.41) after covarying for β‐amyloid. Here, GFAP is linked to Gliosis.