We aimed to evaluate the association between preprocedural D-dimer levels and endovascular and clinical outcomes. We retrospectively reviewed patients with acute intracranial large-vessel occlusion who underwent mechanical thrombectomy. Plasma D-dimer levels were measured immediately before the endovascular procedure. Endovascular outcomes included successful recanalization, first-pass recanalization (first-pass effect (FPE) and modified FPE (mFPE)), thrombus fragmentation, and the number of passes of the thrombectomy device. Clinical outcomes were assessed at 3 months using the modified Rankin Scale. A total of 215 patients were included. Preprocedural D-dimer levels were lower in patients with FPE (606.0 ng/mL [interquartile range, 268.0–1062.0]) than in those without (879.0 ng/mL [437.0–2748.0]; p = 0.002). Preprocedural D-dimer level was the only factor affecting FPE (odds ratio, 0.92 [95% confidence interval, 0.85–0.98] per 500 ng/mL; p = 0.022). D-dimer levels did not differ significantly based on successful recanalization and thrombus fragmentation. The number of passes of the thrombectomy device was higher (p = 0.002 for trend) and the puncture-to-recanalization time was longer (p = 0.044 for trend) as the D-dimer levels increased. Patients with favorable outcome had significantly lower D-dimer levels (495.0 ng/mL [290.0–856.0]) than those without (1189.0 ng/mL [526.0–3208.0]; p < 0.001). Preprocedural D-dimer level was an independent factor for favorable outcome (adjusted odds ratio, 0.88 [0.81–0.97] per 500 ng/mL; p = 0.008). In conclusion, higher preprocedural D-dimer levels were significantly associated with poor endovascular and unfavorable functional outcomes.