Introduction The decompressive craniectomy is a surgical strategy widely used with specific criteria to control the refractory intracranial pressure (ICP). However, it is important to warn about the presence of a postcraniectomy syndrome and analyze the risk-benefit on a long term. Case Report A 72-year-old male patient diagnosed with a subarachnoid hemorrhage secondary to the rupture of an anterior circulation aneurysm that develops vasospasm, secondary ischemia, and edema with signs of herniation that required a decompressive craniectomy on a first step. Afterwards, the aneurysm was approached and he consequently developed hydrocephaly. A ventriculoperitoneal shunt is installed, contralateral to the craniectomy, and progressive sinking of the skin flap, there is neurological deterioration and paradoxical herniation. Its association with the clinical deterioration by bronchoaspiration did not allow the cranioplasty to resolve the ICP decompensation. Conclusions The paradoxical herniation as part of the postcraniectomy syndrome is an increasingly common condition identified in adult patients with cortical atrophy, and who have also been treated with ventricular shunt systems. Timely cranioplasty represents the ideal therapeutic plan once the compromise from the mass effect has resolved to avoid complications derived from the decompressive craniectomy per se.