Kawasaki disease (KD) is a form of acute multisystem vasculitis that presents with various complications, including coronary artery aneurysm. Heart failure and brain damage are rare, but life-threatening complications are associated with KD. Here, we describe a 4-year-old girl who developed intravenous immunoglobulin-resistant KD with both left ventricular failure and acute encephalopathy. On day 8 of the illness, the low left ventricular ejection fraction, mitral regurgitation, and low blood pressure, which required continuous administration of dobutamine, were observed during the treatments for KD, including intravenous immunoglobulin. She also appeared unconscious, where the electroencephalogram showed slow waves of activity in all regions of the brain. The cardiac performance improved after she received plasma exchange for three days. However, her unconsciousness with slow waves of activity on electroencephalogram and fever continued after the plasma exchange. Therefore, she was treated with methylprednisolone pulse, followed by prednisolone, as well as intravenous immunoglobulin. Finally, she recovered without any cardiac or neurological sequelae not only at the time she was discharged, but also throughout the follow-up period. The combination therapy using plasma exchange and methylprednisolone pulse may be a treatment option for severe KD with left ventricular failure and acute encephalopathy complications.