Hydrocephalus by the fourth ventricle outlet obstruction (FVOO) associated with a Chiari malformation type I and syringomyelia is a well-known entity but a rare situation in clinical practice. Although suboccipital craniectomy with the opening of the obstruction membrane appears to be the most physiological approach, by restoring the original pathway of cerebrospinal fluid flow, the endoscopic third ventriculostomy (ETV) represents an important minimally invasive alternative. We report the case of an adult patient with tetra ventricular hydrocephalus by FVOO associated with Chiari malformation and syringomyelia. The ETV alone completely resolved all symptoms, as well as neuroimaging abnormalities on the control magnetic resonance imaging. The ETV is a minimally invasive option for the treatment of hydrocephalus in patients with obstruction at the exit of the fourth ventricle, even in cases associated with Chiari malformation and syringomyelia.