Galectin-1 (GAL1), a widely expressed β‑galacto-side-binding protein, exerts pleiotropic biological functions. GAL1 has been found to be upregulated in many malignancies; yet the role of GAL1 in the pathophysiology of human osteosarcoma (OS) remains uncertain. The present study was carried out to investigate the expression of GAL1 in human OS tissues and to explore its effects on the growth and invasion of OS cells. OS and corresponding adjacent non-cancerous tissues (ANCT) were collected from 30 consecutive cases. The expression of GAL1 was detected by immunohistochemical assay through tissue microarray procedure. Using small hairpin RNA (shRNA)-mediated GAL1 knockdown (Lv-shGAL1) in OS (MG-63 and U-2 OS) cells, we observed the changes in the malignant phenotype in OS cells in vitro and in vivo. As a consequence, the positive expression of GAL1 was significantly higher in OS tissues than that in the ANCT (63.3 vs. 36.7%, P=0.029), and was positively correlated with distant metastasis in the OS patients (P=0.022). Knockdown of GAL1 suppressed cell proliferative activities and invasive potential and induced apoptosis in OS cells with decreased expression of p38MAPK, p-ERK, Ki-67 and matrix metallopeptidase-9 (MMP-9) and increased expression of caspase-3. In addition, the tumor volume in the MG-63 subcutaneous tumor models treated with Lv-shGAL1 was significantly smaller than that in the negative control (NC) group (P<0.01). Altogether, our findings indicate that high expression of GAL1 is associated with distant metastasis of OS patients, and knockdown of GAL1 inhibits growth and invasion of OS cells possibly through inhibition of the MAPK/ERK pathway, suggesting that GAL1 may represent a potential target for the treatment of cancer.