Fenestration of a vertebral artery(VA)is a rare anomaly that has occasionally been associated with the formation of saccular aneurysms, whereas dissection of a limb of the fenestrated artery is an extremely rare occurrence. We report the case of a ruptured dissecting aneurysm of a fenestrated VA. A 56-year-old man presented with acute-onset headache followed by respiratory failure. Computed tomography(CT)revealed diffuse subarachnoid hemorrhage, and CT angiography(CTA)demonstrated fenestration of the left VA and a fusiform aneurysm of the dorsolateral limb of the fenestrated VA. CT after injection of contrast medium revealed dissection of a limb of the fenestrated VA. A comparison of the 3-dimensional digital subtraction angiogram obtained 2 days later with the initial CTA showed that the dissecting aneurysm had shrunk. Coil embolization of the dissecting limb of the fenestrated VA was achieved, and the patient was discharged without neurologic deficit. Further advancements in neuroimaging modalities will provide more opportunities to treat dissecting aneurysms of fenestrated VAs. The relevant clinical characteristics of VA fenestration and the treatment options for a dissecting aneurysm of a limb of the fenestrated VA are also discussed in this report.