Dural arteriovenous fistulas (DAVFs) are abnormal connections between the dural arteries and dural venous sinuses or subarachnoid veins. A rare subtype of DAVF is tentorial DAVF (TDAVF), which is highly aggressive and often exhibits direct retrograde leptomeningeal drainage, increasing the risks of hemorrhage and venous ischemia. Transarterial embolization (TAE) using Onyx has become the preferred treatment method. In Onyx-based TAE, a long embolic material segment should be established within the draining vein past the shunt point. Here, we report a case of a patient with TDAVF who was successfully managed with preservation of the normal deep venous system through a combination of transarterial and transvenous embolization (TVE). A 56-year-old man was referred to our hospital following an abnormal brain imaging finding during a routine checkup. Angiography identified a TDAVF draining into the vein of Galen, categorized as Cognard type III. During Onyx injections, excessive penetration of the draining vein may lead to deep venous system occlusion, potentially causing severe complications. To mitigate this risk, we performed transarterial Onyx injection with TVE using coils, achieving complete occlusion without inducing deep venous infarction. The combination of TVE using coils and Onyx TAE is an effective approach for managing TDAVF, particularly in cases where the distance from the shunt point to the normal venous return is brief, the shunt flow is high, or crucial veins, such as deep cerebral veins, are involved.