Increasing studies have demonstrated that long noncoding RNAs (lncRNAs) play vital roles in tumor development and progression. However, the relationship between osteosarcoma and HIF1AAS2 remains unknown. The expression of HIF1AAS2 and miR-129-5p was detected in osteosarcoma cell lines and samples via qRT-PCR. Cell Counting Kit-8 (CCK-8) and invasion assays were performed to determine cell proliferation and invasion ability, and a dual luciferase reporter assay was performed to determine the interaction between HIF1AAS2 and miR-129-5p. We showed that the expression of HIF1A-AS2 was upregulated in the osteosarcoma samples compared with the expression in noncancerous samples. Moreover, patients with high HIF1A-AS2 expression had a shorter overall survival. Ectopic expression of HIF1A-AS2 enhanced osteosarcoma cell proliferation, cell cycle progression and invasion. We found that overexpression of miR-129-5p decreased the luciferase activity of wild-type (WT) HIF1A-AS2 but not mutant HIF1A-AS2. Ectopic expression of HIF1A-AS2 suppressed miR-129-5p expression in MG-63 cells. We demonstrated that miR-129-5p was downregulated in osteosarcoma and was negatively associated with HIF1A-AS2 expression. Furthermore, ectopic expression of miR-129-5p suppressed osteosarcoma cell proliferation, cell cycle progression and invasion. In addition, overexpression of HIF1A-AS2 promoted cell proliferation, cell cycle progression and invasion of osteosarcoma cells through the modulation of miR-129-5p. These results indicated that HIF1A-AS2 might be a potential therapeutic target for osteosarcoma.