We describe a case of Trousseau's syndrome in a patient with lung carcinoma. A 69-year-old man presented with pleural effusion. Further evaluation revealed EGFR mutation-positive non-small cell carcinoma in the upper lobe with extensive lymph node, bone, and brain metastases. Administration of osimertinib, an EGFR tyrosine kinase inhibitor, resulted in partial tumor response, but caused osimertinib-induced pneumonitis 10 weeks later. Prednisolone restrained lung injury progression and was gradually tapered. However, he presented with impaired consciousness and right hemiplegia. Magnetic resonance imaging revealed a left middle cerebral artery M1 segment occlusion. D-dimer level was elevated to 19.5 μg/mL. In the absence of atherosclerotic or cardiogenic thrombi, these findings led to the diagnosis of Trousseau syndrome. Endovascular therapy, but not tissue plasminogen activator, improved his condition with no recurrences. These treatment strategies are crucial to restore function in patients with potentially disabling cerebral infarction due to Trousseau syndrome.