Background and Purpose- Carotid artery stenting in tandem large vessel occlusion strokes is usually avoided because of the intracranial hemorrhagic risks induced by antiplatelet therapy during thrombectomy interventions. This study aimed to evaluate the incidence of hemorrhagic transformation following thrombectomy in large vessel occlusion strokes patients with atherosclerotic cervical carotid occlusion, associated factors, and clinical relevance. Methods- The TITAN (Thrombectomy in Tandem Lesions) collaboration pooled individual data of prospectively collected multicentric thrombectomy databases for consecutive anterior circulation tandem large vessel occlusion strokes patients who underwent thrombectomy. Hemorrhagic infarction (HI) and parenchymal hematoma (PH) were assessed within 24 hours. Results- Among 289 patients with atherosclerotic cause, 66 (24.7%) patients developed HI and 38 (14.2%) PH. Intracranial carotid occlusion, diabetes mellitus, absence of prior intravenous thrombolysis, and complete extracranial carotid occlusion were independent predictors of HI. Similar predictors were found for PH with addition of higher baseline National Institutes of Health Stroke Scale and Alberta Stroke Program Early CT Score <7. No detrimental effect of HI on 90-day clinical outcome was found. The occurrence of PH was associated with increased mortality rates (adjusted odds ratio, 2.63; 95% CI, 1.05-6.59; P=0.039) and had no detrimental effect on 90-day modified Rankin Scale 0 to 2 (adjusted odds ratio, 0.52; 95% CI, 0.20-1.28; P=0.25). Conclusions- Incidence of PH after tandem large vessel occlusion strokes thrombectomy is equivalent to those reported in the literature data for isolated occlusions. Similar predictors were found for PH and HI within 24 hours, whereas acute carotid artery stenting and antiplatelet therapy were not, suggesting an aggressive endovascular treatment of tandem occlusions.