Trousseau syndrome (TS) is a thrombosis disorder characterized by a hypercoagulable state linked to underlying malignancies, resulting in various thrombotic events such as deep vein thrombosis, pulmonary embolism, and arterial thrombosis. This syndrome serves as a crucial indicator of malignancy and can often be the first sign of an underlying tumor. In this case, we report a case of gastrointestinal malignant tumor as the first onset, and analyzes its clinical characteristics to improve the clinicians' understanding of this kind of disease. A 69-year-old woman was admitted to the hospital 4 times in 1 month for cerebral infarction. The patient was admitted several times with a new cerebral infarction lesion and a high D-dimer level, a persistently positive fecal occult blood test, and a gastrointestinal tumor was later found. The patient was diagnosed with TS, attributed to her underlying malignancy. During hospitalization, the patients were treated with aspirin for antiplatelet, esomeprazole for protection of gastric mucosa, atorvastatin for lowering blood lipids, butylphthalein for improvement of collateral circulation, edaravone dextrocamphorol for scavenging oxygen free radicals, and betahistine hydrochloride tablets for preventing dizziness. The patient's condition improved significantly after initial treatment, but died of the tumor a year after discharge. Currently, TS has a complex and varied clinical presentation and is relatively difficult to diagnose, especially in patients with an unknown tumor history. Focus should be placed on patients with recurrent cerebral infarctions and increased D-dimer levels, and anticoagulation may be an effective treatment for patients with TS.