Objective：To investigate the relationship between serum programmed cell death factor 4（PDCD4）levels and neurological deficits as well as prognosis in patients with acute ischemic stroke（AIS）. Methods：A retrospective analysis was conducted on 110 AIS patients admitted to the Department of Neurology，the Second Affiliated Hospital of Nantong University between June 2023 and March 2024. Based on the National Institutes of Health Stroke Scale（NIHSS）scores，patients were divided into a mild group（n=70）and a moderate to severe group（n=40）. According to the modified Rankin Scale（mRS），patients were further divided into a good prognosis group（n=69）and a poor prognosis group（n=41）. The demographic data（age，sex，diabetes history，etc.）and clinical data（neutrophil count，lymphocyte count，neutrophil-to-lymphocyte ratio，etc.）of each group of patients were collected. Serum PDCD4 levels were measured using an enzyme-linked immunosorbent assay（ELISA），and their correlations with NIHSS scores，mRS scores， and other inflammatory markers were analyzed. Logistic regression was employed to identify risk factors for moderate - to - severeneurological deficits and poor prognosis in AIS patients. Receiver operating characteristic（ROC）curves were used to evaluate the effectiveness of serum PDCD4 levels in predicting the degree of neurological deficit and prognosis of AIS patients. Results：Serum PDCD4 levels were significantly higher in AIS patients with moderate -to - severe neurological deficits or poor prognosis compared to those with mild deficits or good prognosis. PDCD4 levels showed positive correlations with NIHSS scores，mRSscores，procalcitonin， high - sensitivity C - reactive protein（Hs -CRP），and neutrophil -to -lymphocyte ratio. After adjusting for confounding factors，PDCD4 remained an independent risk factor for AIS. ROC analysis demonstrated that serum PDCD4 had high predictive value for both neurological deficit severity and prognosis. Conclusions：Elevated serum PDCD4 levels are strongly associated with moderate - to - severe neurological deficits and poor prognosis in AIS patients，serving as an independent predictive biomarker for clinical outcomes.