There is no effective therapy for acute exacerbation of idiopathic pulmonary fibrosis. Recently, it has been suggested that the pathology of acute exacerbation of idiopathic pulmonary fibrosis is indicative of hypercoagulable status. We studied the efficacy of recombinant human thrombomodulin (rhTM) α for acute exacerbation of idiopathic pulmonary fibrosis. Of a total of 29 patients, we retrospectively compared the background and prognosis between the 12 patients in the rhTM-administered group and the 17 patients in the non-rhTM-administered group. One- and three-month-survival rates of the groups were 75% and 67% in the rhTM-administered group and 46% and 40% in the non-rhTM-administered group, respectively (log-rank test, p=0.154). Bleeding complications in the rhTM-administered group were not observed. Recombinant human thrombomodulin α has the possibility of improving prognosis in acute exacerbation of idiopathic pulmonary fibrosis.