Purpose <p>We aimed to describe a rare case of a posterior cerebral artery (PIC) dual origin from a vertebral artery (VA) fenestration and to propose a detailed embryological reasoning on this anomaly. Among the anomalies of intracranial arteries, fenestrations are not uncommon and they may be associated with aneurysms and arterio-venous malformations. The VA is one of the most frequent locations for fenestrations, being more common in extracranial that in intracranial segment and due to different embryological mechanisms. Moreover, among the cerebellar arteries, the posterior-inferior cerebellar artery (PICA) demonstrates the greatest anatomical variability regarding its origin, course, and branching pattern. In some cases, the differentiation between fenestrations and duplications is quite subtle.</p> Methods <p>We are presenting the case of an association of anomalies with a huge fenestration of the V4 VA and PICA originating from one of the limbs of the fenestration. This was an incidental finding during a computed tomography angiography (CTA) performed because of sudden headache. The anatomical and embryological features of this finding are discussed in detail.</p> Conclusions <p>The reported anomaly may have different names (fenestration vs duplication) and different embryological origins among the persisting primitive anastomoses pertaining to the lateral spinal artery or posterior spinal artery systems.</p>