Juvenile myelomonocytic leukemia (JMML) is an aggressive clonal hematopoietic disorder of infancy and early childhood. About 15% of these patients have CBL mutation, which is usually a germline mutation with a high incidence of CBL syndrome. Conventional chemotherapy would be little benefit to these children, but epigenetic therapy with the DNA-hypomethylating agents can make a great difference in disease control. Here we report two infants diagnosed as JMML with CBL mutation. One case was treated with 6-mercaptopurine intermittently, but she was often hospitalized for pneumonia since the disease was not well controlled. The other one was treated with decitabine. He achieved clinical complete remission (CR) after three cycles of decitabine (20mg/m2/d×5 days, repeated every 4 weeks). Unfortunately, the patient’s symptoms were recurrent two months later. Thus, JMML patient with CBL mutation has a good clinical response to decitabine, while how and how long it could be used remain to be further explored.