Aortitis is a broad term describing inflammation of the aorta. The most common causes of aortitis are the large-vessel vasculitides giant cell arteritis and Takayasu arteritis. Other etiologies include aortitis associated with other autoimmune disorders, infectious causes, and paraneoplastic and idiopathic cases. We describe a rare case of a large-vessel arteritis occurring in association with chronic myelomonocytic leukemia (CMML). A 68-year-old female with recent diagnosis of CMML presented to our office for evaluation of abnormal chest computed tomography (CT) that showed inflammation surrounding the entirety of thoracic and abdominal aorta, consistent with aortitis. In the absence of other evident causes of large-vessel vasculitis, we attributed this finding to a paraneoplastic autoimmune phenomenon and started treatment with systemic glucocorticoids. This rare case emphasizes the need to recognize autoimmune complications in CMML and treat the inflammation along with the primary malignancy promptly.