Pleural effusion has various causes. In the setting of aortic stenosis, new onset pleural effusion is generally considered as a consequence of heart failure. Here, we describe a 50-year-old male patient who had been followed with aortic stenosis for 30 years. During his admission he presented with exertional dyspnea and pleuritic chest pain. He had no other symptoms or findings of cardiac failure. Complete blood count revealed neutrophilic leukocytosis, a normal hemoglobin level and normal platelet count. Left sided pleural effusion was noted on the posteroanterior chest X-ray. Examination of the pleural fluid revealed myeloid blasts. Bone marrow aspiration smear and flow cytometric analysis of the bone marrow and pleural fluid were consistent with acute myeloid leukemia.