Increased head and neck cancer (HNC) survival requires attention to long-term treatment sequelae. Irradiated HNC survivors have a higher ischemic stroke risk. However, the pathophysiology of radiation-induced vasculopathy is unclear. Arterial stiffness could be a biomarker. This study examined alterations in intima-media thickness (IMT) and stiffness-related parameters, shear wave (SWV) and pulse wave velocity (PWV), in irradiated compared to control carotids in unilateral irradiated patients. Twenty-six patients, median 40.5 years, 5-15 years after unilateral irradiation for head and neck neoplasms underwent a bilateral carotid ultrasound using an Aixplorer system with SL18-5 and SL10-2 probes. IMT, SWV, and PWV were assessed in the proximal, mid, and distal common (CCA) and internal carotid artery (ICA). Plaques were characterized with magnetic resonance imaging. Measurements were compared between irradiated and control sides, and radiation dose effects were explored. CCA-IMT was higher in irradiated than control carotids (0.54 [0.50-0.61] vs. 0.50 [0.44-0.54] mm, p = 0.001). For stiffness, only anterior mid-CCA and posterior ICA SWV were significantly higher in the irradiated side. A radiation dose-effect was only (weakly) apparent for PWV (R : end-systolic = 0.067, begin-systolic = 0.155). Ultrasound measurements had good-excellent intra- and interobserver reproducibility. Plaques had similar characteristics but were more diffuse in the irradiated side. Increased CCA-IMT and SWV in some segments were seen in irradiated carotids. These alterations, even in young patients, mark the need for surveillance of radiation-induced vasculopathy. clinicaltrials.gov ( https://clinicaltrials.gov/ct2/show/NCT04257968 ).