Beyond SCAT-3 symptom score, GFAP at the acute postinjury time point was associated with the classification of athletes with concussion from contact controls (β = 12.298; 95% CI, 2.776-54.481; P = .001) and non–contact sport controls (β = 5.438; 95% CI, 1.676-17.645; P = .005). Here, GFAP is linked to concussion.