RATIONALE: Rosette-forming glioneuronal tumor (RGNT) is a rare primary nervous system tumor, with limited treatment guidelines due to its rarity, especially in the brainstem. This report presents a unique case of brainstem RGNT treated with gamma knife radiosurgery (GKRS). PATIENT CONCERNS: A 35-year-old woman sought medical attention after sudden syncope and rapid decline in consciousness. Magnetic resonance imaging revealed a mass in the pineal region, extending to the brainstem and thalamus. Due to the critical location, only partial resection of the pineal tumor was possible, leaving most of the residual tumor in the vital brainstem area, requiring urgent intervention to control its growth and prevent sudden complications. DIAGNOSES: Postoperative histopathological results confirmed a diagnosis of RGNT. INTERVENTIONS: The patient underwent 25 Gy/5 fractions of GKRS using the frameless Gamma Knife ICON™ (Elekta) device, as confirmed by cone-beam computed tomography scans for precise dose distribution and patient alignment. OUTCOMES: GKRS was performed successfully and safely. The tumor significantly shrank 3 months post-GKRS, and the patient experienced symptom relief without any adverse effects. LESSONS: GKRS is considered an effective modality for RGNT in high-risk brainstem areas, minimizing risks while controlling tumor growth and alleviating symptoms. In addition, the frameless Gamma Knife ICON™ device enhanced patient comfort and treatment precision. GKRS offers a noninvasive alternative for similar RGNT cases.