An 8-year-old boy developed anorexia, fatigue, and fever. Laboratory examination revealed a high white blood cell (WBC) count of 145×10/μL with 97.5% abnormal promyelocytic cells that contained Auer bodies. Faggot cells were seen. He was diagnosed with acute promyelocytic leukemia. Later, a chromosome analysis showed 46,XY,t(15;17)(q22;q12). Promyelocytic Leukemia-retinoic acid receptor α-fused gene and chimeric mRNA were confirmed by fluorescence in situ hybridization and reverse transcriptase polymerase chain reaction, respectively. He was complicated with disseminated intravascular coagulation (DIC) and his fibrin and fibrinogen degradation product at the onset was 37.6 μg/mL. Human recombinant thrombomodulin (rTM) was started for DIC. After dexamethasone was administered at a dose of 8 mg/m to prevent all-trans retinoic acid syndrome on day 1, all-trans retinoic acid was started at a dose of 45 mg/m on day 4. Cytarabine (100 mg/m/d) and daunorubicin (45 mg/m/d) were started on day 9. The WBC count gradually increased to 270×10/μL on day 8, and then decreased beginning on day 9. DIC improved after the initiation of chemotherapy and only minor petechia was noted. DIC did not become worse even after rTM was stopped on day 8. The risk of DIC and bleeding is high in the early stage of treatment for acute promyelocytic leukemia, especially in patients with a high WBC count. In our patient, rTM may have prevented fatal DIC and made it possible to safely administer induction chemotherapy.