Background: Leukemic infiltration of the optic nerve is a neuro-oncologic emergency and also a sign of extramedullary central nervous system relapse. It presents a clinical dilemma in the early stages due to multiple differentials. Patients with leukemia receive radiation and chemotherapy are thus, susceptible to inflammatory, toxic, and infectious causes of optic neuropathy, besides infiltration with tumor cells. Clinical Description: A 15-year-old boy treated for acute lymphoblastic leukemia (ALL) and in remission for 7 months, presented with the unilateral decreased vision for 7 days. A structured evaluation was done, comprising visual acuity, color vision, field of vision, fundus, ophthalmoscopy, ultrasound b-scan, and magnetic resonance imaging of the orbit. The final diagnosis was leukemic infiltration of the optic nerve. Cerebrospinal fluid (CSF) analysis confirmed the presence of atypical lymphocytes. Management: The patient was diagnosed with extramedullary relapse of ALL. Since there are no standard guidelines, a literature review was performed, and the treating team decided to start the patient on stand-alone chemotherapy. Symptomatic resolution became apparent within 10 days. On follow-up, the optic nerve lesion resolved with residual gliosis in the surrounding retina. The CSF has become clear, and the patient is now considered to be in remission. Conclusion: It is important to use a structured clinical approach coupled with investigations to recognize the ocular involvement of ALL (especially in younger patients). There is a need for a regular routine ophthalmological examination in patients in remission for early detection of a relapse. There is a strong felt need for pediatric hemato-oncologists to plan research in this area to generate data so that recommendations for the management of extramedullary relapses are formulated.