Mixed connective tissue disease (MCTD) is characterized as a benign rheumatic disease with a favorable response to therapy. When pulmonary hypertension is a complication, however, it is often reported to be fatal. A 32-year-old female patient with MCTD who had developed rapidly progressive pulmonary hypertension and disseminated intravascular coagulopathy was admitted to our hospital and was successfully treated with corticosteroids and anticoagulants. The failure of microcirculation due to coagulopathy is considered to be one of the possible entities of pulmonary hypertension.