OBJECTIVE The aim of this study was to present a case of basilar artery (BA) formed by persistent primitive trigeminal artery (PPTA), which was diagnosed using digital subtraction angiography (DSA). CONCLUSIONS PPTA is a common branching variation of embryological origin. The prevalence of PPTA ranges between 0.1 and 0.6%. It has been reported that PPTA typically joins the BA proximally and supplies the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA) or posterior inferior cerebellar artery (PICA) branches. This is the first report of a case where the vertebral artery (VA) terminates in the PICA, and PPTA forms the BA and solely supplies the posterior circulation. CONCLUSIONS No study or case report has been identified in the English literature on persistent primitive trigeminal artery serving as the sole source of blood supply to basilar artery alone.