PURPOSE: To report a relatively rare case of huge pilocytic astrocytoma of the optic nerve and optic chiasm causing eyeball subluxation. CASE SUMMARY: An eight-year-old male presented with proptosis and visual loss in the left eye for one year. The radiological findings showed a 2.9 x 2.7 x 4.2-cm tumor on the left optic nerve and optic chiasm. For diagnosis and treatment, the patient underwent tumor resection and enucleation. Pathohistological analysis of the tumor specimen revealed pilocytic astrocytoma, which is classified by the World Health Organization as a grade I astrocytic tumor. CONCLUSIONS: Astrocytoma is a tumor of the brain that affects children more often than adults. In general, gross-total resection of pilocytic astrocytoma is expected to be curative due to the non-invasive feature of the tumor. Considering pilocytic astrocytoma as differential diagnosis of orbital tumor in children with symptoms of rapidly progressive proptosis and decreased visual acuity is important because occurrence in the optic nerve and optic chiasm is possible.