The purpose of this study was to evaluate the technical efficacy and safety of transvenous Onyx embolization for dural arteriovenous fistulas (DAVFs) with concomitant transvenous balloon protection of the venous sinus when transarterial route failed or was not feasible. Between September 2010 and December 2016, thirty-six patients presenting with intracranial DAVFs underwent transvenous balloon-assisted Onyx embolization. The technical efficacy, treatment-related complications, and angiographic and clinical outcomes were reviewed from our prospectively maintained DAVF database. According to the Cognard classification, 11 patients presented with clinically symptomatic Cognard type I; 11 cases with Cognard type IIa; 10 cases with Cognard type IIb and 4 cases with Cognard type IIa+b. Complete angiographic occlusion of the DAVFs at the latest follow-up (mean 18 months after transvenous embolization) was achieved in 28 patients (77.8%), near-complete angiographic occlusion with minimal residual fistula in 5 patients (13.9%) and significant flow reduction of the DAVF in 2 patients (5.6%) and residual fistula for further treatment in 1 (2.8%) patient. Total clinical cure or remission of the pre-treatment symptoms was achieved in 31 patients (31/36, 86.1%; 26 and 5 cases respectively). Affected venous sinus was preserved in 28 patients, intentionally occluded in 7 patients and gradually occluded in 1 patient. There were no immediate or long term persistent complications after treatment. Transvenous Onyx embolization of dural arteriovenous fistulas with combined transvenous balloon protection of the venous sinus is safe and effective in achieving high occlusion rate, low embolization-related complications and satisfactory clinical outcomes.