Nail dystrophy is an underrecognized manifestation of lung involvement in chronic graft-versus-host disease (cGVHD) in children. We present a case of a 17-year-old male with a history of allogeneic bone marrow transplant who developed nail dystrophy 17 months post-transplant in the context of lung cGVHD. Clinical findings included polydactylous longitudinal erythronychia, onychorrhexis, and distal nail splitting. Management of cGVHD-associated nail dystrophy is primarily symptom-driven. This case highlights the importance of routine nail examinations in patients with cGVHD.