We presented an unusual case of a young woman who suffered an ischaemic stroke while receiving chemotherapy postsurgery for breast cancer. No cause was identified at that time and a year later an incidental pulmonary arteriovenous malformation (PAVM) was diagnosed during an MR review of her breasts. This was confirmed on the CT and she subsequently underwent successful endovascular embolisation. Ischaemic stroke as a presenting symptom of an undiagnosed PAVM or hereditary haemorrhagic telangiectasia is rare. PAVM is a clinically important and treatable cause of ischaemic stroke and should therefore be considered in young patients with ischaemic stroke, with or without concurrent venous thrombotic risk factors. As far as we are aware, this is the first reported incidental finding of PAVM on MR of the breast.