Indirect carotid-cavernous fistulas (iCCFs) are shunts between meningeal branches of the internal carotid and/or the external carotid arteries and the cavernous sinus. They account for 83% of all carotid-cavernous fistulas (CCFs). Symptomatic iCCFs and those with increased risk of hemorrhage should be treated. Transvenous endovascular treatment is the preferred treatment modality. However, in complex cases, a combination of transarterial and transvenous approaches (multimodal treatment) is required. A middle-aged woman presented with signs of increased intraocular pressure, blurry vision, diplopia, left proptosis, chemosis, conjunctival injection, ptosis, and cranial nerve VI palsy. Imaging confirmed the presence of a Barrow type D and Thomas type 4 iCCF with cortical venous reflux (CVR). The patient underwent transarterial and transvenous onyx embolization of the shunt, achieving a complete obliteration of the fistula. No complications occurred and the patient had a satisfactory postprocedural evolution. Multimodal onyx embolization is an effective option for the treatment of a complex symptomatic iCCF. If CVR is identified, these lesions should be promptly treated to prevent hemorrhage secondary to rupture.