Abstract: Objective To investigate the effects of miR-181b on the migration and invasion of osteosarcoma cells. Methods Three cultured osteosarcoma cell lines and MG-63 cells transfected with miR-181b inhibitor were examined for miR-181b expression using qRT-PCR analysis. The cell migration and invasion of the transfected cells were assessed with Transwell assay. The targets of miR-181b were predicted using a miRNA target prediction software and the results were verified with luciferase reporter assay. The target protein expression in osteosarcoma cells lines was determined by Western blotting, and the cell migration and invasion changes following inhibition of miR-181b or its target protein were assessed using Transwell assay. Results All the 3 osteosarcoma cells lines showed significantly up-regulated miR-181b expression. Inhibition of miR-181b expression obviously suppressed the migration and invasion of MG-63 cells. Based on luciferase reporter assay, N-myc downstream regulated gene 2 (NDRG2) was identified as the direct target gene of miR-181b, and inhibition of NDRG2 expression significantly reversed the effect of miR-181b on cell migration and invasion in MG-63 cells. Conclusion miR-181b is over-expressed in osteosarcoma cells, and inhibition of miR-181b, which directly targets NDRG2, can suppress the migration and invasion of osteosarcoma cells.