Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of the hematopoietic stem cell that is exceptionally rare in the first five years of life, particularly as a secondary malignancy. This report describes a case of secondary CML in a four-year-old female occurring after AML treatment. Interestingly, CML developed while on immunosuppression for a heart transplant due to anthracycline-induced cardiomyopathy. Pediatr Blood Cancer 2015;62:166–168. © 2014 Wiley Periodicals, Inc.