Previous studies demonstrated that a subpopulation of cancer cells, which are CD133 positive (CD133+) feature higher invasive and metastatic abilities, are called cancer stem cells (CSCs). By using tumor cells derived from patients with lung adenocarcinoma, we found that galectin-1 is highly overexpressed in the CD133+ cancer cells as compared to the normal cancer cells (CD133-) from the same patients. We overexpressed galectin-1 in CD133- cancer cells and downregulated it in CSCs. We found that overexpression of galectin-1 promoted invasiveness of CD133- cells, while knockdown of galectin-1 suppressed proliferation, colony formation and invasiveness of CSCs. Furthermore, tumor growth was significantly inhibited in CSCs xenografts with knockdown of galectin-1 as compared to CSCs treated with scramble siRNAs. Biochemical studies revealed that galectin-1 knockdown led to the suppression of COX-2/PGE2 and AKT/mTOR pathways, indicating galectin-1 might control the phenotypes of CSCs by regulating these signaling pathways. Finally, a retrospective study revealed that galectin-1 levels in blood circulation negatively correlates with overall survival and positively correlates with lymph node metastasis of the patients. Taken together, these findings suggested that galectin-1 plays a major role on the tumorigenesis and invasiveness of CD133+ cancer cells and might serve as a potential therapeutic target for treatment of human patients with lung adenocarcinoma.