Cholangiocarcinoma (CCA) is a fatal disease with high resistance to anticancer drugs. This is probably in part due to enhanced resistance to apoptosis. We have previously shown that galectin-3 (Gal-3), a beta-galactoside-binding lectin, is highly expressed in CCA tissues. In this study, we demonstrated further that Gal-3 plays a direct role in anti-apoptosis regardless of the apoptotic insults. The anti-apoptotic activity and chemoresistance of CCA cells were related to Gal-3 expression level. Suppression of Gal-3 expression with siRNA stimulated apoptosis. siGal-3-K626 transiently depleted Gal-3 expression to the baseline and dramatically induced apoptosis, while siGal-3-K402 suppressed Gal-3 expression by 50% and provoked cell apoptosis, but only under apoptotic insults (hypoxic conditions or short UV radiation). These actions were reversed in Gal-3 overexpressing CCA cells. The correlation between the degree of anti-apoptotic activity and the level of endogenous Gal-3 was demonstrated. Suppression of Gal-3 expression in CCA cells with siGal-3-K402 significantly enhanced apoptosis induced by cisplatin or 5-fluorouracil by approximately 10 times, whereas overexpression of Gal-3 led to an increased resistance to drugs. In summary, the present study showed that the cellular level of Gal-3 might contribute to the anti-apoptotic activity and chemoresistance of CCA cells. Hence, Gal-3 expression level in cancer cells or tissues may be a marker for predicting chemotherapeutic response, and Gal-3 may be a specific gene-targeting therapy option for treating CCA.