Multisystem inflammatory syndrome in children, or paediatric inflammatory multisystem syndrome, is a rare disorder characterised by a hyperinflammatory response to a previous severe acute respiratory syndrome coronavirus 2 infection. The course of the illness is usually relatively mild; nevertheless, severe cases have also been reported. We present a rare case of a 3-year-old girl with fulminant myocarditis with complete heart block associated with multisystem inflammatory syndrome in children. The condition was life-threatening and required intensive treatment of bradycardia with isoprenaline and the percutaneous implantation of an electrode for temporary pacing. Additionally, anti-inflammatory treatment with intravenous immunoglobulins and glucocorticosteroids was administered, leading to a rapid recovery with complete resolution of heart conduction abnormalities. In cases of fulminant myocarditis with complete heart block, prompt and intensive bradycardia treatment, combined with appropriate anti-inflammatory treatment, may be crucial for the patient’s prognosis.