Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy (TMA)-related disease that manifests as a triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury (AKI) and is caused by uncontrolled activation of the complement system. We report the case of a 61-year-old woman with acute type A aortic dissection that subsequently developed into aHUS. The hematologic disorders underlying aHUS improved after treatment with the complement inhibitor eculizumab. It is important to consider aHUS when a patient clinically develops a triad of microangiopathic hemolytic anemia, thrombocytopenia, and an increasing creatinine level following cardiovascular surgery.