Introduction: The pseudo-tumor cerebri (PTC) is defined as the idiopathic or benign intracranial hypertension (IH), complaints of which cannot be explained in a different way. PTC is an exclusion diagnosis, in which the neuroophtalmopathology of IH cannot be determined. The patients with PTC may have complaints such as headache, nausea, vomiting, temporary blurred vision, and mild-level vision loss or unilateral or bilateral abducens nerve paralysis may develop. The radiological examination of patients yields normal results. In case that IH develops due to any reason, the enlargement is seen in optic nerve sheath diameter (ONSD) in the acute period. Case reports: 14 year-old patient, who has been diagnosed for PTC in our unit, optic nerve sheath diameter (ONSD) measurement and follow-up of pressure change of whom have been performed by using ultrasonography (USG) method, is presented in order to discuss the contribution of this non-invasive method to diagnosis, treatment, and observation processes. Conclusion: USG and ONSD measurement in PTC cases may be effective and reliable monitoring method as much as invasive methods.