Krüppel-like factor 8 (KLF8) is a transcription factor that is important in the regulation of the cell cycle and has a critical role in oncogenic transformation and epithelial to mesenchymal transition (EMT). EMT is a key process in tumor metastasis. Although overexpression of KLF8 has been observed in a variety of human tumor types, the role of KLF8 in human osteosarcoma is yet to be elucidated. The present study aimed to investigate the biological impact of KLF8 on Saos-2 osteosarcoma cells. KLF8 gene expression was knocked down in vitro using a lentivirus-mediated small interfering (si)RNA method. Cell proliferation and cell cycle distribution were evaluated using 3-(4,5)-dimethylthiahiazo(-z-yl)-3,5-di-phenytetrazoliumromide and colony formation assays, and flow cytometry, respectively. Cell invasion was analyzed using a Transwell® invasion assay. Knockdown of KLF8 was found to significantly inhibit proliferation and invasion in osteosarcoma cells. These data suggest that KLF8 may exhibit an important role in osteosarcoma tumorigenesis and that KLF8 may be a potential therapeutic target for the treatment of osteosarcoma.