Embolic stroke due to pulmonary vein thrombosis is rare but may be associated with lung and left atrial tumours, pulmonary surgery, atrial fibrillation and radiofrequency ablation. It is very rarely idiopathic. A 23-year-old man developed acute onset of a left partial third nerve palsy and left ataxic hemiparesis. His MR scan of the brain showed an acute infarct in the left midbrain and left thalamus. CT angiogram found no steno-occlusive disease and transthoracic echocardiogram was normal. However, a transoesophageal echocardiogram showed a hyperechoic mass projecting from the right inferior pulmonary vein, confirmed on cardiac MR scan to be a right inferior pulmonary vein thrombus. A cardiac loop recorder did not capture an atrial arrhythmia. CT scan of the chest found no significant abnormality in the pulmonary parenchyma. Investigations for hypercoagulable state were negative. He took dabigatran for 6 months with complete resolution of thrombus.