Human malignant mesothelioma (MM) is an insidious and aggressive neoplasm, arising from mesothelial cells of the plura. The disease is usually associated historically with occupational exposure to asbestos. As the prognosis is very poor, novel therapeutic strategies are needed to be developed. Recent works in stem cell biology suggest that some cancers contain stem-like cells (cancer stem cells, CSCs). In human cancers, CSCs have already been identified in most of the malignant tumors. As the stem cell characters of cancer are supposed to be the major reason for therapy-resistance, understanding these properties in MM cells is very important. For this purpose, we first established mouse xenograft model of MM by direct transplantation of primary tumor tissue. We established 6 mouse serial transplantation models and a new cell line TUM1. Next, we searched for stem cell markers such as side population (SP) and specific CD markers using the existing cell lines and TUM1. We found that many cell lines contain SP cells, suggesting that they keep one of the stem cell properties. We also found that CD9 and CD24, putative cancer stem cell markers, are expressed heterogeneously in many of these mesotheolioma cells. Furthermore, we found that SP and CD24-positive cells proliferated by asymmetric cell division-like manner. Interestingly, expression of CD26 closely correlated with that of CD24 in many of these mesothelioma cells. In addition, these surface marker-positive cells generated larger tumors than negative cells in mouse transplantation assay, and exhibited drug-resistance, higher proliferation, and invasive potentials in vitro. Moreover, the expressions of several stem cell genes were significantly up-regulated in the stem cell culture and TUM1 formed spheroid colony. These results suggest that MM harbors several stem cell signatures and they are candidates for new therapeutic targets.