Objective: Newly-diagnosed disturbed glucose metabolism is highly prevalent in non-diabetic patients with transient ischemic attack (TIA) or ischemic stroke, and increases the risk of recurrent stroke. Diabetes mellitus is associated with atherosclerosis. We aimed to assess whether newly-diagnosed disturbed glucose metabolism is associated with atherosclerosis as well. Research design and methods: Patients with a recent TIA or ischemic stroke were classified in three groups based on glucose levels and use of antidiabetic drugs. Pre-existent diabetes mellitus was defined as the use of antidiabetic drugs prior to the event. Newly-diagnosed disturbed glucose metabolism was defined as two or more disturbed glucose tests: fasting plasma glucose level ≥ 5.6 mmol/L, 2-hour post-load glucose level ≥ 7.8 mmol/L, and/or glycosylated hemoglobin level ≥ 39 mmol/mol. We used CT-angiography to assess stenosis in the carotid artery bifurcations and calcification volume in the aortic arch, carotid bifurcations and intracranial carotid arteries. The relation between glucose groups and measures of atherosclerosis was expressed as odds ratios and beta coefficients with corresponding 95% CI, adjusted for potential confounders. Results: Of the 1217 patients, 384 (32%) had newly-diagnosed disturbed glucose metabolism, and 210 (17%) had pre-existent diabetes mellitus. Newly-diagnosed disturbed glucose metabolism was independently associated with stenosis ≥ 50% (aOR (95%CI) 1.15 (1.04-2.20)). Pre-existent diabetes mellitus was associated with stenosis ≥ 50% and with calcification volume in all regions, especially in patients without the use of cholesterol-lowering drugs prior to the event. Conclusions: Our study shows that newly-diagnosed disturbed glucose metabolism in patients with a recent TIA or ischemic stroke is associated with more severe extra-and intracranial atherosclerosis, similar to pre-existent diabetes mellitus.