OBJECTIVE AND IMPORTANCE: Brain stem and cerebellar edema rarely have been described as the principal manifestation of hypertensive encephalopathy. In addition, secondary hydrocephalus has been described in only a few cases in the literature. We present an unusual case of posterior fossa swelling and hydrocephalus resulting from hypertensive encephalopathy. CLINICAL PRESENTATION: A 53-year-old man presented with increased shortness of breath, headache, and visual changes, which had been worsening for several months. Blood pressure on presentation was 253/140 mm Hg. Neuroradiological studies revealed brain stem swelling predominantly affecting the pons, with compression of the adjacent cisterns and fourth ventricle and resultant hydrocephalus. The diagnosis of brain stem glioma was briefly entertained. INTERVENTION: The patient's blood pressure was brought under control with medical management, and he was treated with dexamethasone for 48 hours. Subsequent neuroradiological studies revealed decreased posterior fossa edema as well as marked improvement in the hydrocephalus. CONCLUSION: Hypertensive encephalopathy can present principally in the posterior fossa and can give rise to obstructive hydrocephalus. Invasive treatment of the hydrocephalus is not necessarily required in this clinical setting because reduction of the blood pressure may result in rapid improvement of the hydrocephalus.