Background: Surgical interventions including ventriculostomy and ventriculo-peritoneal shunt were usually administrated in pineal germ cell tumor patients with symptomatic hydrocephalus. Considering higher sensitivity of germinoma to anti-tumor therapy, we explored emergency irradiation as non-invasive measure in this situation. Methods: Data of 35 germinoma patients with symptomatic hydrocephalus who received emergency irradiation of 3.4 Gy/2f were studied retrospectively. The maximum width of frontal horn and the minimum width of trunk of corpus callosum (TCC) were measured to evaluate hydrocephalus changing. Besides, mean deviation (MD) of Humphrey perimetry was employed to evaluate visual field defect. Correlations between hydrocephalus changing and clinical factors, including age, percentage of tumor regression, radiographic re-evaluation interval, and serum beta-human chorionic gonadotropin (β-HCG) level, were analyzed. Results: The median maximum diameter and volume of pineal lesions was 27 mm (range 10-55 mm) and 6.5cm3 (range 0.4-74.1 cm3), respectively. At median 8 days after irradiation, the median percentage of tumor remission was 55% (range 10-100%). The median maximum width of FN and the median minimum width of TCC were 11.6 mm and 39.0 mm, and 8.0 mm and 31.4 mm, before and after irradiation, respectively. The improvement of both parameters reached significant level (p < 0.001). However, none clinical factor was found to have correlation with their improvement. In 14 patients with paired data of pre- and post-irradiation MD, its change did not reach the significant level for both eyes. All patients successfully received subsequent chemoradiotherapy without surgical intervention. Conclusions: Emergency irradiation of 3.4 Gy/2f was an effective non-invasive measure to relief hydrocephalus in pineal germinoma patients. © 2019 The Author(s).