Granulocyte colony-stimulating factor(G-CSF)is useful for preventing febrile neutropenia induced by chemotherapy. Recently, some cases of aortitis have been reported following administration of G-CSF. Here, we present a case of aortitis induced by pegfilgrastim(peg-G)use during neoadjuvant chemotherapy for treating breast cancer. A 61-year-old woman with breast cancer(cT2N1M0, stage ⅡB, triple negative)started neoadjuvant chemotherapy FEC(100). Eleven days after the third course of peg-G administration, the patient developed a fever and general malaise. Blood test results showed an increase in inflammatory markers and severe anemia. The symptoms were not controlled with antibiotics. Blood and urine culture test results were negative. Computed tomography revealed remarkable wall thickening of the aorta. Therefore, we suspected aortitis induced by peg-G. The symptoms rapidly improved with prednisolone therapy. The possibility of aortitis should be considered for those with fever or raised inflammatory markers following the use of G-CSF. Steroids can be used for the treatment of G-CSF-induced aortitis.