An 81-year-old man with prostate cancer (cT3aN0M0), who had been undergoing hormonal therapy for 4 years and had maintained low prostate specific antigen levels, developed metastasized pelvic lymph nodes. A tissue biopsy revealed neuroendocrine differentiation of prostate cancer in the metastatic lymph nodes. Consequently, chemotherapy with carboplatin＋etoposide was initiated. During the first course, filgrastim was administered for 2 days due to a drop in his neutrophil count to 230/μl. During the second course, pegfilgrastim was administered as prophylaxis on day 4. However, on day 10 of the second course, he started to develop a fever and fatigue. Suspecting infection, antibiotics were administered, but failed to ameliorate his symptoms. On day 14, plain computed tomography revealed signs of aortic inflammation. Given the lack of improvement even after one week of antibiotic therapy, steroid treatment was initiated on the suspicion of granulocyte colony-stimulating factor (G-CSF) -induced aortitis, which rapidly improved his symptoms. Therefore, when encountering a case in which a fever remains unresponsive to antibiotics during chemotherapy with G-CSF agents, a differential diagnosis of aortic inflammation caused by G-CSF agents needs to be considered.