BACKGROUND: Red blood cell distribution width (RDW) is an inflammatory marker potentially linked to stroke-associated pneumonia (SAP). This study assessed RDW's role in predicting SAP, mortality, and poor outcomes in acute ischemic stroke (AIS) patients treated with thrombolysis. METHODS: A retrospective analysis (2015-2022) of AIS patients treated with thrombolysis examined admission RDW levels. Outcomes included SAP, in-hospital (IHM) and 3-month mortality, and poor functional outcomes. Associations were analyzed using multivariable logistic regression, with predictive performance assessed via area under a receiver operating characteristic curve (AuROC), net reclassification index (NRI), and integrated discrimination improvement (IDI) metrics. RESULTS: Of 345 patients, 70 (20.3 %) developed SAP. A 1-SD increase in RDW was associated with SAP (adjusted odds ratio [aOR]: 1.73
95 % CI: 1.27-2.35), IHM (aOR: 2.14
95 % CI: 1.43-3.21), and 3-month mortality (aOR: 1.74
95 % CI: 1.19-2.56). The association was stronger in non-diabetics and those under 65. Although RDW did not improve the AuROC for SAP or mortality predictions, it significantly improved the NRI and IDI (p <
0.05). CONCLUSIONS: RDW is independently associated with increased risk of SAP, IHM, and 3-month mortality in AIS patients treated with thrombolysis, suggesting its potential as a prognostic marker.