Introduction <p>Large artery atherosclerosis is a relevant cause of ischemic stroke. Beyond carotid artery stenosis <i>≥</i> 50%, causative in etiological classification of stroke, non-stenosing plaques are an increasingly reported cause of stroke with embolic pattern.</p> Methods <p>We are presenting the case of a 56 years old woman presenting with a first symptomatic multifocal ischemic stroke in the right internal carotid artery (ICA) territory on 2018 and a finding of asymptomatic past vascular injury in the same vascular territory on neuroimaging studies. Extended etiological search, including extra- and intracranial vascular investigations, cardiological studies with prolonged heart rhythm monitoring, screening for acquired and genetic prothrombotic conditions failed to reveal any cause. In 2021, the patient went again for a recurrent symptomatic stroke in right ICA territory and Computed Tomography Angiography (CTA) found a huge floating thrombus on a very small plaque at the right ICA, already known from the previous CTA. Treatment with low-molecular-weight-heparin at anticoagulant dosage was started until documentation of thrombus resolution and finally the patient underwent stenting. The clinical and neuroradiological follow-up until now did not show changes.</p> Discussion <p>Even very small carotid plaques might be associated with stroke and the putative mechanism of artery-to artery embolism from superimposed thrombus is often hypothesized but seldom imaged. This could lead to a misclassification of stroke etiology and to a non-negligible rate of atherothrombotic embolic stroke of undetermined source (ESUS) with higher risk of recurrence.</p> Conclusions <p>Atherothrombotic stroke may come from non-stenosing plaques and artery-to artery embolism is a common mechanism.</p>