Background: Intracranial neurenteric cysts are rare, benign, and slow-growing tumors. However, we encountered a pediatric case that the cyst expansion occurred in a short period of time resulting in rapid deterioration of the patient's symptoms. Case Description: A previously healthy 7-year-old girl had a week history of dysarthric speech and diplopia along with headaches. Her magnetic resonance images (MRI) showed an abnormal cystic mass in her brainstem. Her symptoms were deteriorated for 1 month and her second MRI revealed an enlargement of the cystic lesion. The tumor biopsy and cyst drainage were carried out and histopathological examination of the cyst wall showed columnar epithelium containing ciliated cells. The final diagnosis of her tumor was neurenteric cyst. Conclusion: We report a pediatric case of a neurenteric cyst in the brainstem, which expanded in a short period, and review this rare entity.