The development of hematologic malignancy in the presence of chronic lymphocytic leukemia (CLL) is rare. We present a case of acute myeloid leukemia (AML) with del(7q) occurring in a patient with a 4-year history of untreated CLL. Application of flow cytometry and immunohistochemistry allowed for characterization of two distinct coexisting malignant cell populations. After undergoing induction and consolidation chemotherapy, the patient achieved complete remission of AML with the persistence of CLL. Allogeneic transplantation was pursued given his unfavorable cytogenetics. Subsequent matched unrelated donor allogeneic stem cell transplantation resulted in full engraftment and complete remission, with no evidence of AML or CLL. Due to a scarcity of reported cases, insight into treatment and prognosis in cases of concurrent AML and CLL is limited. However, prognosis seems dependent on the chemosensitivity of AML. CLL did not have a detrimental effect on treatment or transplant outcome in our case. This is the first reported case of concomitant de novo AML and CLL to undergo allogeneic transplantation. The patient remained in complete hematologic and cytogenetic remission of both malignancies over a year after transplantation.