Post-stroke induction of alpha-synuclein (AS), a neuronal protein implicated in the pathogenesis of Parkinson's disease (PD), has been demonstrated to induce secondary brain damage after cerebral ischemia. Therefore, understanding the expression and pathogenic modifications of AS is clinically meaningful for evaluating the prognosis of stroke. Here, 54 patients with acute ischemic stroke (AIS) and 55 controls were enrolled. Different forms of AS in red blood cells (RBCs), including hemoglobin-bound AS (Hb-AS), oligomeric AS (O-AS), and serine 129-phosphorylated AS (pS-AS), were measured using ELISA methods. Compared with controls, significantly increased levels of Hb-AS, O-AS, and pS-AS were observed in AIS patients. The levels of O-AS and pS-AS were both positively correlated with that of Hb-AS. However, no correlation was observed between 0-AS and pS-AS. The levels of all three forms of AS were associated with increased risk of AIS diagnosis. Receiver operating characteristic (ROC) curves revealed that the three forms of AS yielded a moderate discriminative power (AUC ranging from 0.67 to 0.71 in discriminating AIS patients from controls, with varying sensitivity (0.41 similar to 0.61), specificity (0.78 similar to 0.90), PPV (0.73 similar to 0.81), and NPV (0.61 similar to 0.68)). These findings suggest that RBC AS can be a potential biomarker for evaluating AS changes in the brain of AIS patients.