Background <p>Posterior circulation stroke carries a high risk of morbidity and mortality, and the presence of vertebral artery collaterals may influence stroke severity and outcome. Duplex ultrasonography is a noninvasive tool for assessing these collaterals. This study aimed to investigate the role of extracranial and transcranial duplex in assessing vertebral artery collaterals in patients with posterior circulation stroke and to explore their relationship with risk factors and prognosis. Thirty-five patients of both sexes with posterior circulation stroke were enrolled. At baseline, all patients underwent detailed medical history, general and neurological examination; magnetic resonance imaging (MRI) brain with diffusion cut, extracranial and transcranial duplex, assessment with the expanded National Institutes of Health Stroke Scale (e-NIHSS), and the modified Rankin scale (mRS). Follow-up evaluation was performed using e-NIHSS and mRS one year after stroke onset.</p> Results <p>Vertebral artery collaterals were detected in five (14.3%) of patients all of whom had cervical collaterals. Absence of collaterals was significantly associated with older age, diabetes mellitus (DM), hypertension (HTN), atrial fibrillation (AF), and smoking. Patients with collaterals had statistically significant smaller infarct size, lower baseline e-NIHSS scores, and lower follow-up e-NIHSS and mRS scores one year after stroke, indicating better prognosis and outcomes.</p> Conclusions <p>Transcranial duplex is a good, inexpensive, bedside tool for assessment of vertebral artery collaterals in posterior circulation stroke. Patients with collaterals tended to be younger and less frequently diabetic, hypertensive, AF or smokers, with smaller infarct size, lower baseline e-NIHSS and better prognosis and outcome.</p>