<p>Choroidal fissure cysts (CFCs) are rare cystic lesions arising in the region of the choroidal fissure. Most are discovered incidentally and remain clinically silent. Rapid interval enlargement with associated mass effect is distinctly uncommon. We report an infant with a rapidly enlarging choroidal fissure cyst. A cystic lesion in the choroidal fissure was first detected on neuroimaging at 6&#xa0;months of age. Follow-up imaging at 10&#xa0;months demonstrated marked cyst enlargement with compression of adjacent brain tissue. The patient subsequently underwent neuroendoscopic cyst fenestration with fistulization. Postoperative imaging showed a substantial reduction in cyst size. A review of the literature indicates that choroidal fissure cysts are generally benign, stable lesions; however, a small subset may enlarge progressively and present with increased intracranial pressure, seizures, focal neurological deficits, or hydrocephalus. MRI is essential for diagnosis and differential diagnosis. Periodic imaging surveillance is appropriate for asymptomatic patients with stable radiological findings, whereas surgical intervention should be considered in cases of progressive enlargement or symptom development. Neuroendoscopic cyst fenestration offers several advantages, including minimal invasiveness, establishment of communication between the cyst cavity and cerebrospinal fluid pathways, and avoidance of long-term shunt dependence.</p>