This study presents the rare case of an intraosseous dural arteriovenous fistula (DAVF) draining into the diploic veins in the left frontal bone with high-flow feeder, successfully treated with transarterial Onyx embolization. A 59-year-old male exhibited mild right hemiparalysis and aphasia without prior head trauma, surgery, or venous sinus thrombosis. Imaging identified DAVF, fed by the bilateral superficial temporal arteries, left middle meningeal artery, and left occipital artery, draining retrogradely solely through the diploic veins into the superior sagittal sinus, causing cortical venous reflux (CVR). Treatment involved Onyx embolization under flow control, preventing Onyx (Medtronic, Irvine, CA, USA) migration and achieving complete DAVF occlusion, resolving the neurological deficits. This case highlights the clinical significance of diagnosing and managing DAVF draining exclusively into the diploic veins, emphasizing the effectiveness of Onyx embolization in such cases.