<p>  Parasellar lesions such as pituitary adenoma and craniopharyngioma may present with obstructive hydrocephalus due to tumors inside the third ventricle, and urgent treatment for acute hydrocephalus is required when the neurological symptoms worsen rapidly. In the treatment of acute hydrocephalus and tumor removal, it is essential that the chosen strategy be based on the patient’s condition and the nature of the tumor or, in the case of emergency surgery, based on factors such as the specialized neurosurgeons and instruments that the hospital can provide. We report 6 cases of parasellar tumors that required treatment for acute hydrocephalus. In two cases of pediatric craniopharyngioma, the third ventricular tumor at the obstruction site was partially removed in emergency surgery to palliatively resolve hydrocephalus, and radical tumor removal was then performed several months later. In 3 patients with adult craniopharyngioma, infantile immature teratoma, and pituitary adenoma with a third ventricular lesion, emergency surgery for hydrocephalus was performed solely with the placement of ventricular drainage or an Ommaya reservoir, and radical tumor removal was performed a few days later. Instead of emergency hydrocephalus surgery, one patient with pituitary adenoma presenting with progressive obstructive hydrocephalus underwent early endonasal surgery to treat the hydrocephalus and the tumor in a single stage. In the case of pediatric craniopharyngioma, the relief of acute hydrocephalus may improve nutritional status, helping the patient to gain weight, and contribute to the growth of the craniofacial structure. It may therefore be possible to wait for several months for extended endonasal surgery, which is a radical operation. Pituitary adenomas that extend to the third ventricle, unlike normal cases, directly invade the subarachnoid space beyond the diaphragm and are often prone to bleeding, making surgery difficult. Care must be taken as the superior hypophyseal artery distributing the optic chiasm runs within the tumor. Although acute hydrocephalus with parasellar tumors is rare, it is known to occur. It is important to select the appropriate surgical procedure in consideration of the nature of the tumor and the overall treatment plan.</p>