Giant cell arteritis (GCA), the most common form of systemic vasculitis in adults, preferentially involves large and medium-sized arteries in patients over the age of 50. The classic manifestations are headaches, jaw claudication, polymyalgia rheumatica, and visual symptoms. Acute myeloid leukemia (AML) is a hematopoietic stem cell disorder characterized by a block in the differentiation of hematopoiesis, resulting in the growth of a clonal population of neoplastic cells or blasts. This malignant alteration in hematopoietic stem cells leads to a loss of normal hematopoietic function, which, if left untreated, typically leads to death within weeks to months of its clinical presentation. Although there have been reports of CLL or CML accompanied by several kinds of autoimmune vascular diseases, such as polymyalgia rheumatica, GCA, or necrotizing temporal arteritis, no studies have reported a case of AML with GCA. We experienced an 80-year-old male patient who developed AML 6 years after the diagnosis of GCA. He was under the use of oral glucocorticoid, hydroxychloroquine, and methotrexate at the time of the diagnosis of the AML. This is the first case in Korea to report GCA accompanied by AML.