Oral hairy leukoplakia (OHL) is caused by the reactivation of a previous Epstein-Barr virus (EBV) infection in the epithelium of the tongue. Most lesions are characterized by corrugated whitish patches on the lateral border of the tongue. It is frequently associated with AIDS, but cases in patients with other immunosuppressed states have also been reported. In leukemia patients, OHL is rarely encountered, and appears only after chemotherapy. We report a case of OHL which occurred as a presenting sign of acute myeloid leukemia (AML) in a previously healthy 15-year-old child. A 15-year-old boy presented with a whitish patch on the left lateral border of the tongue. The biopsy specimen revealed papillomatosis, hyperkeratosis, acanthosis and ballooning degeneration in the stratum spinosum. The patient was EBV seropositive, and PCR analysis of EBV DNA in the lesional tissue was positive. After the diagnosis of OHL in dermatologic department, the patient was referred to pediatrics due to the abnormal peripheral blood smear, and was diagnosed with AML.