Mixed Connective Tissue Disease(MCTD) is an overlap syndrome characterized by a combination of clinical features similar to those of systemic lupus erythematosus(SLE), scleroderma, polymyositis, and rheumatoid arthritis and unusually high titers of circulating antibody to a nuclear ribonucleoprotein antigen. The mean age of presentation is 37 years and 80% of patients are female. Cardiac involvement is less common in adults but may be more frequent in children. Pericarditis is the most common finding,' other findings include mitral valve prolapse, myocarditis and congestive heart failure. We experienced a case of pericarditis and asymmetric LV hypertrophy in a 33-yr-old postpartum woman with mixed connective tissue disease, who admitted to our hospital because of fever, dyspnea and chest discomfort, which was diagnosed by echocardiography and selorogic study. She was treated with oral prednisolone and aspirin and presented symptoms improved and pericardial effusion was disappeared.