The association of neurofibromatosis 1 (NF1), juvenile xanthogranulomas (JXG), and juvenile myelomonocytic leukemia (JMML) has been previously reported. We describe herein this triad in a Caucasian male infant with a pathogenic mutation in the NF1 gene (neurofibromin). The clinical course from initial presentation to final diagnosis is detailed; the physical features and hematologic characteristics are discussed. The patient underwent bone marrow transplantation and is currently in remission. Children with concurrent cutaneous café-au-lait and JXG lesions should be evaluated and monitored closely for the possible development of JMML.