Cerebrospinal fluid (CSF) drainage is a routinely used adjunct in operation of thoracoabdominal aortic aneurysm (TAAA), which may reduce the incidence of perioperative paraplegia by improving spinal cord perfusion. Neurological complications of CSF drainage have been reported, possibly due to excessive CSF drainage, and acute subdural hematoma (SDH) in particular may lead to catastrophic complications. We present a rare case of acute SDH due to CSF drainage that was not excessive, after TAAA repair in a patient with Marfan syndrome, who recovered without invasive treatment.