BACKGROUND: First-pass reperfusion (FPR) in stent-retriever thrombectomy is associated with favorable outcomes in acute ischemic stroke patients due to large vessel occlusion (LVO). This study systematically evaluated the clinical significance of the FPR in stent-retriever thrombectomy for acute ischemic stroke patients. METHODS: A total of 543 patients with acute LVO were enrolled in three prospective, randomized, and multicenter stent thrombectomy trials. A successful FPR was defined as when a patient had a modified thrombolysis in cerebral infarction (mTICI) score of 2b/3 with a single stent-retriever thrombectomy. All patients were divided into FPR and non-FPR groups. The patients' baseline characteristics and clinical outcomes were analyzed. Moreover, the predictors of a successful FPR were identified. RESULTS: Among the 224 FPR and 319 non-FPR patients, the FPR group had significantly better clinical outcomes with a lower NIHSS score at discharge and a lower mRS score and a mortality rate at 90 d ( P < 0.05) and, meanwhile, had reduced complications rates of embolization into new territory and symptomatic intracranial hemorrhage. When the 95 patients with mTICI 2b reperfusion exclusively in the FPR group were compared with patients in the non-FPR group, the FPR cohort with mTICI 2b reperfusion demonstrated significantly superior clinical outcomes. Multivariate analysis identified BGC use and M2-MCA occlusion as independent predictors of FPR success. CONCLUSIONS: First-pass recanalization (FPR) is associated with improved clinical outcomes. Balloon guide catheter (BGC) utilization significantly enhances FPR. Patients with M2-segment middle cerebral artery (M2-MCA) occlusions have a greater likelihood of FPR success.