BACKGROUND Massive retinal gliosis (MRG) is a rare benign intraocular tumor that results from the proliferation of well-differentiated glial cells in response to long-standing pathological processes, including glaucoma, trauma, chronic inflammation, vascular disorders, and congenital anomalies. This lesion is considered to be nonneoplastic and occurs ≥10 years after the predisposing insult. It usually affects children and can mimic other conditions, including uveal melanomas, vasoproliferative tumors of the retina, astrocytic hamartomas, and retinal hemangioblastomas. CASE REPORT We present a case of infant MRG with severe left eye microphthalmia. An 11-month-old boy was presented by his parents in the Oculoplastic Unit of a teaching university hospital with bilateral incomplete cryptophthalmos and small globes. An enucleation of the left globe was carried out to stimulate orbital bone growth and to improve the cosmetic outcome. The histopathological examination revealed a microphthalmic globe with sclerocornea and disorganized intraocular anterior segment structures. The retina was dysplastic with proliferating spindle-shaped glial cells showing fibrillar eosinophilic cytoplasm and filled most of the vitreous cavity. The glial origin of the cells was confirmed by the immunohistochemical markers (glial fibrillary acidic protein and synaptophysin), supporting the diagnosis of MRG. The optic nerve was markedly hypoplastic. CONCLUSIONS MRG is a rare intraocular tumor that is clinically difficult to diagnose. A definite diagnosis can be made only on the basis of a histopathological examination and immunohistochemical markers.