We report the case of a 2-year-old boy with langerhans cell histiocytosis who developed vincristine (VCR)-induced unilateral ptosis and recovered on treatment with pyridoxine and pyridostigmine. He was treated with LCH TRAIL (Initial treatment) chemotherapy regimen. Two days after the fifth dose of VCR, he presented with unilateral ptosis. VCR as an antineoplastic drug causes neurotoxicity frequently. Neurological examination revealed unilateral ptosis, without pupillary or other oculomotor dysfunction. The other cranial nerves and peripheral nerves examinations were normal. Cranial magnetic resonance imaging and cerebrospinal fluid examination were normal. The unilateral ptosis markedly improved after two weeks of pyridoxine and pyridostigmine treatment and completely resolved after 3 weeks and there was no further recurrence of ptosis on follow up.