Introduction: Patients with atrial fibrillation (AF) can experience ischemic stroke despite adequate anticoagulant therapy. The secondary prevention strategy of these so-called “resistant strokes” is empirical. Since about 90% of patients with ischemic stroke due to atrial fibrillation have thrombus in left atrial appendage (LAA) we sought to explore the possibility that resistant stroke could have a LAA morphology resistant to anticoagulants. Case Report: A 77 years old man affected by AF experienced two cardioembolic ischemic stroke while on anticoagulants. The study of LAA showed a windsock-like morphology in the proximal part while distally the LAA presented a cauliflower morphology with a large amount of pectinate muscles and blood stagnation. The precise characteristics of LAA were properly understood integrating images obtained by cardiac CT, transesophageal echocardiography, and selective angiography. A high risky LAA for thrombus formation was diagnosed and its occlusion (LAAO) as an add-on therapy to anticoagulants was proposed and performed. Six month follow-up was uneventfully. Conclusion: The systematic study of LAA in patients with resistant-stroke could help to identify LAA malignant morphology. The efficacy on stroke recurrence of the combined therapy (anticoagulants plus LAAO) is worthy to be tested in randomized trials.