Orbital venous malformations are low-flow lesions resulting from vascular dysgenesis during development. Patients may present with vision loss, proptosis accentuated by Valsalva, and/or painful spontaneous thrombosis. The preferred treatment for symptomatic lesions is embolization combined with excision. A 34-year-old male presented to our institution from an outside emergency department with a diagnosis of presumed idiopathic orbital inflammation. For the prior month, he had been experiencing left orbital pressure, subjective eye bulging, and both diplopia and blurry vision when in peripheral gaze or when bending over. Despite initial improvement with steroids, his symptoms recurred with tapering. Visual acuity was reduced to 20/25, but pupils and motility remained normal. Biopsy demonstrated a vascular lesion characterized by fibroadipose tissue with histologically unremarkable blood vessels, and cerebral arteriography showed no high-flow components. A diagnosis of orbital venous malformation was made. He then underwent intraoperative angiography and Onyx embolization followed by excision via a transcaruncular approach. Two prior reports have described the use of Onyx in venolymphatic malformations. This report highlights a detailed approach to defining flow characteristics pre- and intraoperatively and expands upon our understanding of the use of Onyx for such cases.