Background and Purpose—Coagulopathy is an important cause of stroke in cancer patients. However, underlying mechanisms and clinical factors related to coagulopathy remain unclear. We hypothesized that certain characteristics of cancer affect coagulopathy in patients with lung cancer and ischemic stroke.Methods—Consecutive patients with active lung cancer and acute ischemic stroke were prospectively studied. Volume and pattern of acute brain infarcts and plasma levels of circulating tumor extracellular vesicles (EVs) were measured using flow cytometry. In vitro experiments investigated the pathophysiological mechanisms underlying cancer-associated coagulopathy.Results—Of 114 patients, 95 (83.3%) had an adenocarcinoma cell type and 95 (83.3%) had distant metastasis. Acute brain infarct volumes were larger and circulating EV levels were higher in patients with an adenocarcinoma cell type than in those with other cell types. The presence of metastasis was not associated with infarct volume or circulating EV levels. Coagulation assays demonstrated dose-dependent shorter clotting times after treatment with EVs from adenocarcinoma cell lines than with the use of EVs from squamous cell carcinoma. These findings were confirmed by coagulation assays using circulating EVs from patients with adenocarcinoma and stroke and from those with conventional stroke mechanisms.Conclusions—Our findings indicate that cancer cell type is associated with circulating EV levels and coagulopathy in patients with lung cancer and stroke.