BACKGROUND The central nervous system (CNS) is a rare point of origin for mature or immature teratomas. However, immature teratomas are extremely rare. CNS teratomas have been known for poor patient prognosis and recovery and also reduce survival. However, chemoradiotherapy has been reported to increase patient survival. CASE REPORT This study presents a rare giant immature teratoma invading a newborn infant's brain tissue and CNS. The tumor was surgically removed, and in a further 1-year follow-up, it did not need chemotherapy or radiotherapy according to alpha-fetoprotein (aFP) level and other serum markers. The teratoma had affected multiple loci of his brain's left hemisphere, including parietal, frontal, temporal, and occipital lobes. A teratoma was diagnosed lateral to the midline, which is not common in CNS teratomas, as they mainly occur in or near the midline. The tumor was excised completely. The patient was followed up for 1 year, and no further recurrence was observed. CONCLUSIONS Early diagnosis and treatment of immature teratomas are essential in patient prognosis. Chemotherapy is not always needed, but complete surgical removal and patient follow-up are always a necessity. In addition, adequate follow-up of these patients is critical to evaluate their further treatment plan and recurrence risk.