Juvenile myelomonocytic leukemia (JMML) is a rare hematologic malignancy in children. Its presentations include anemia, thrombocytopenia, monocytosis, skin rash, marked hepatomegaly, and/or splenomegaly. Fever and respiratory involvement are common. Here, we report a case of a premature neonate with initial symptoms of respiratory distress. She gradually developed clinical manifestations of JMML that mimicked neonatal sepsis. Three weeks after birth, JMML was diagnosed. This is the first reported case of JMML presenting in a premature infant in Taiwan.