Background and aims: Intracranial atherosclerotic plaque is associated with ischemic strokes without substantial stenosis, and needs better characterization. We aim to investigate the clinical significance of intracranial plaque without substantial stenosis by high resolution vessel wall MRI (vwMRI) through a systematic review of existing studies. Methods: Studies investigating intracranial arterial atherosclerotic plaques without substantial stenosis in acute ischemic stroke patients using vwMRI were systematically identified by searching the PubMed and Medline database and article reference lists. Study characteristics were recorded, the methodological quality of eligible studies was assessed, relevant clinical data were extracted, and collective data was analyzed. Results: Twenty-one studies were identified as eligible. 463 patients were included without stenosis of the intracranial arteries, and 651 patients were included with stenosis <50%. The prevalence of intracranial plaque revealed by vwMRI among acute/subacute ischemic stroke patients with non-stenotic Magnetic Resonance Angiography (MRA) was 50.6% (95% confidence interval (CI), 46.1%–55.1%). The prevalence of <50% MRA stenotic culprit plaque among acute/subacute ischemic stroke patients with a clinical diagnosis of intracranial atherosclerosis was 51.2% (95% CI, 38.4%–64.0%). Plaques features, including wall enhancement, positive remodeling, intraplaque hemorrhage, plaque location and eccentricity, were associated with acute stroke, progressive motor deficits and unfavorable overall functional outcomes. Conclusions: Intracranial high-risk plaque with zero or mild degree of stenosis is more prevalent than previously acknowledged, and is associated with ischemic stroke and unfavorable outcome. VwMRI can identify the high-risk plaque features, which may act as a promising tool to better risk stratify these patients. © 2019 Elsevier B.V.