Giant cell arteritis may lead to catastrophic, large-vessel complications from chronic vascular wall inflammation without prompt diagnosis and treatment. We describe a rare case of acute aortic dissection without preceding aneurysm secondary to histologically confirmed giant cell arteritis (GCA) in an 85-year-old female with a four-year history of polymyalgia rheumatica and temporal arteritis diagnosed per biopsy six months prior to presentation. The literature is reviewed and the clinical implications of this case are discussed.