Tenascin and decorin are components of the extracellular matrix (ECM) that are implicated in cell proliferation in tumors. Here, we propose that abnormal expression of stromal ECM may play an important role in the progression of intrahepatic cholangiocarcinoma, which is characterized by desmoplastic reaction. To explore this hypothesis, we performed immunohistochemical analysis in order to examine the expression and distribution of tenascin and decorin in 75 cases of intrahepatic cholangiocarcinoma. In the intratumoral stroma, positive staining for tenascin was observed in 51 (68%) cases, and positive staining for decorin was observed in 61 (81%) cases. However, at the invasive front, positive staining for tenascin was found in 23 (31%) cases, and positive staining for decorin was found in 6 (8%) cases. Decorin staining was not correlated with aggressive behavior of intrahepatic cholangiocarcinoma, whereas intratumoral tenascin staining was correlated with lymphatic permeation and proliferative activity measured by Ki67. Tenascin staining at the invasive front was associated with tumor size, lymphatic permeation, lymph node metastasis, and proliferative activity and appeared to be a useful prognostic factor by univariate analysis, although it was not an independent prognostic factor. These results indicate that tenascin plays a role in tumor progression in cases of intrahepatic cholangiocarcinoma and that tenascin expression, especially at the invasive front, may be a useful marker in evaluating an unfavorable prognosis in patients with intrahepatic cholangiocarcinoma.