Background Onyx is a liquid non-adhesive viscous embolic agent ideal for slow targeted injections which is currently approved for the treatment of intracranial aneurysms and arteriovenous malformations.

Methods We performed a single-center retrospective analysis of consecutive patients who underwent off-label use of Onyx as the single embolic agent for the treatment of traumatic or infectious pseudoaneurysms involving the cerebral or cranial vasculature.

Results A total of nine pseudoaneurysms treated by Onyx embolization were identified. Six of the pseudoaneurysms were post-surgical, one of the pseudoaneurysms was traumatic and two were infectious in nature. The mean pseudoaneurysm size was 5.9 mm (range 2–10 mm). Onyx-34 was used in all cases. Following treatment there was complete exclusion of all pseudoaneurysms including their inflow and outflow zones.

Conclusions Our experience demonstrates the efficacy and applicability of the use of Onyx in the treatment of complex traumatic and mycotic pseudoaneurysms involving the cerebral and cranial vascular tree.