GPT-4o achieved moderate diagnostic accuracy in classifying stroke etiology from de-identified records. Accuracy was highest for cardioembolic and small-vessel strokes, with lower precision in mixed or undetermined etiologies. Cardioembolic stroke demonstrated the highest sensitivity (0.96) and F1 score (0.85), followed by lacunar stroke with sensitivity of 0.92 (95%) and F1 score of 0.82 (95%). Specificity was consistently high across all etiologies (>0.84), with cardioembolic and severe ECAD achieving 0.79 and 0.96, respectively.Moderate performance was observed for arterial dissection (F1: 0.70, sensitivity: 0.93) and EVAS (F1: 0.69, sensitivity: 0.79).