Osteosarcoma (OS) has emerged as the most common primary musculoskeletal malignant tumor which affects children and adolescents. A growing number of relevant studies have shown that many micro-RNA5 (miRNAs) play a vital regulatory role in the etiology of various types of cancer. miR-1258 has been widely studied in various cancers, but there have been few studies of its role in OS. In this present study, miR-1258 expression was dramatically decreased in OS tissues as well as OS cell lines. In addition, decreased expression of miR-1258 was significantly associated with malignant clinical manifestations and poor clinical prognosis of patients with OS. Moreover, upregulation of miR-1258 significantly inhibited cell proliferation as well as promoting cell cycle arrest at GO/G1. AKT3 was identified as a direct target of miR-1258 by binding to its 3'-UTR, and miR-1258 was negatively correlated with AKT3 expression in clinical OS tissues. AKT3 was evidently upregulated in OS tissues and cells and upregulation of AKT3 accelerated the progression of OS. Moreover, through a series of rescue experiments, we demonstrated that AKT3 can abolish the role of miR-1258 in suppressing proliferation as well as regulating the cell cycle in OS cells. In conclusion, our results suggest that the miR-1258-AKT3 axis may be a promising prognostic marker and therapeutic target for human OS. (C) 2019 Elsevier Inc. All rights reserved.