Takayasu's arteritis (TA) rarely occurs in infants. There are only four reports on TA in children below 1 year of age, revealing diversity of its symptoms. We describe a 7-month-old female infant hospitalized for hectic fever, irritability, high acute phase indices, and coronary artery dilatations found on echocardiography, which suggested Kawasaki disease (KD). Despite of standard treatment, rapid development of thoracic and abdominal aorta aneurysms occurred, while coronary artery abnormalities regressed. The initial diagnosis was changed for TA. Subsequently implemented glucocorticosteroids led to clinical and laboratory normalization. However, 2 months after treatment discontinuation, TA relapsed. Glucocorticosteroid therapy was restarted with additional introduction of intravenous immunoglobulins (IVIG), resulting in full and stable remission lasting over 1 year. Thus, diagnosis and treatment of infant TA pose a big challenge to physicians. TA onset in infants may mimics KD. Prolonged glucocorticosteroids and IVIG administration can be recommended in the youngest patients with TA.