MicroRNAs (miRNAs) deregulation has been reported to play important roles in tumorigenesis and tumor development through the regulation of their targets in Osteosarcoma (OS). Hence, fully understanding the biological roles and mechanisms of OS-related miRNAs may contribute to the development of novel therapeutic targets for patients with this disease. In this study, we found that miR-34b expression was downregulated in OS tissues and cell lines. The resumption of miR-34b expression led to a significant reduction in cell proliferation and invasion of OS. Meanwhile, Cyclin D1 (CCND1) was identified as a direct target of miR-34b in OS through bioinformatics analysis, luciferase reporter assay, quantitative reverse-transcription PCR (RT-qPCR) and Western blot analysis. The results of the present study demonstrated that low miR-34b expression is involved in OS formation and progression, suggesting that miR-34b/CCND1 axis may serve as a potential therapeutic target in OS oncogenesis.