A fusiform aneurysm of the superior cerebellar artery (SCA) is rare and mainly occurs at the proximal segment. A 71-year-old female patient was admitted to our institution with a subarachnoid hemorrhage. Angiography revealed dominance of both SCAs with aplasia of both the posterior inferior cerebellar artery and a fusiform aneurysm at the cortical segment of the left SCA involving the bifurcation site. Bypass connecting the left occipital artery to the inferior branch of the left SCA was performed, followed by trapping and clipping of the proximal and distal parts of the aneurysm, respectively. Blood flow was maintained in a retrograde manner from the inferior branch to the superior branch. She was discharged with no neurologic deficits and continues to be followed up by our department as an outpatient. This is the first report of a treatment method for a fusiform aneurysm located in the cortical segment of the SCA.