Giant serpentine aneurysms (GSAs) are defined as partially thrombosed giant aneurysms with persistent serpentine vascular channels. Surgical management of these rare lesions is difficult because of their large size, complex structure, and unique hemodynamics. The authors report two cases of patients harboring GSAs with mass effect, which were managed effectively with endovascular treatment. The first patient was a 48-year-old man who presented with left homonymous hemianopsia caused by a GSA involving the terminal portion of the right internal carotid artery. The second patient, a 10-year-old boy, presented with tetraparesis from compression of the cervicomedullary junction by a GSA of the right vertebral artery. In each case, after confirming collateral flow by temporarily occluding the proximal artery, the aneurysm was trapped by placement of Guglielmi detachable coils at the sites at which the serpentine channels entered and exited the aneurysm. The midportion of each channel was isolated completely without packing, to maximize resorption of the devascularized mass. Mass effect and clinical symptoms rapidly improved in both cases, with no associated morbidity. We recommend endovascular trapping as a safe and effective therapeutic option for GSAs.