Acute myeloid leukemia (AML) developing in patients with chronic lymphocytic leukemia (CLL) is very uncommon and usually associated with prior treatment. Acute promyelocytic leukemia (APL) accounts for a very small proportion of treatment-associated AML. So far, there has been only one reported case of APL occurring post radiation for prostate cancer in a patient with CLL. We report herein the first case of APL and CLL presenting concomitantly in an untreated patient. Evaluation of peripheral blood and bone marrow aspirate with immunohistochemistry, flow cytometry, and FISH to confirm two morphologically, molecularly and genetically distinct leukemic populations characteristic of APL and CLL is required. APL is a hematologic emergency, and aggressive management is vital to a successful therapeutic outcome. Standard treatment is with All-trans retinoic acid (ATRA) and anthracycline-based regimen, whether the process is de novo or therapy-related. Due to increased incidence of secondary malignancies in CLL patients, active surveillance is necessary.