A 65-year-old woman with rheumatoid arthritis treated by tocilizumab (TCZ) presented with tongue squamous cell carcinoma. While surgery was performed without any complications the aspiration pneumonia rapidly worsened by postoperative day 2 and severe pulmonary suppuration in the right lung field with infection-induced systemic inflammatory response syndrome (SIRS) was diagnosed. Antibiotic and respirator treatment improved her condition. The anti-inflammatory effect of TCZ may mask the symptoms and signs of severe infection with SIRS.