Cardiac disease is a significant complication of childhood oncologic therapy. We report the case of a 14-year-old female with acute promyelocytic leukemia who developed symptomatic cardiomyopathy only 4 months into treatment with a combination of daunomycin and all-trans retinoic acid (ATRA). Despite cessation of daunomycin, she demonstrated fluctuating systolic function in relation to ATRA administration. Improvement and deterioration in systolic function on echocardiogram and serum B-natriuretic peptide levels were seen while receiving ATRA 1 week on and 1 week off, respectively, during the maintenance phase of therapy.