Juvenile myelomonocytic leukemia (JMML) is a distinct myeloproliferative malignancy of early childhood with a varied clinical presentation that may include failure to thrive, malaise, fever, bleeding, pallor, lymphadenopathy, and hepatosplenomegaly. Skin, pulmonary, and gastrointestinal involvement have also been reported. There are no reports of central nervous system (CNS) involvement at diagnosis of this disease. This is a report of a 21-month old boy who had a right facial paresis at presentation. A brain mass was demonstrated on magnetic resonance imaging and cerebrospinal fluid analysis confirmed CNS leukemic infiltration. We report the presence of CNS infiltration as a part of the natural course of JMML and provide a review of the literature.