Background: Graft-versus-host disease is the most common complication after allogeneic hematopoietic stem cell transplantation. While ocular graft-versus-host disease typically manifests as dry eye syndrome and anterior segment involvement, posterior segment complications are rare. Previously reported posterior segment complications in graft-versus-host disease have been limited to acute presentations with significant functional visual impairment. Methods: A 41-year-old man developed progressive retinal nerve fiber layer and ganglion cell layer loss four years after allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia. The patient had established chronic graft-versus-host disease with cutaneous involvement and ocular surface disease. Results: Despite preserved visual acuity and visual fields, and only subtle functional involvement on visual evoked potentials, optical coherence tomography revealed significant reduction in retinal nerve fiber layer thickness and ganglion cell layer. Magnetic resonance imaging showed no optic nerve or brain abnormalities. Conclusions: This case describes an uncommon presentation of chronic, subclinical posterior segment involvement in chronic GVHD and suggests that optical coherence tomography may detect progressive structural retinal changes in the absence of clinically evident visual impairment, supporting its potential role in longitudinal monitoring.