Long noncoding RNAs (lncRNAs), widely expressed in mammalian cells, play pivotal roles in osteosarcoma (OS) progression. Nevertheless, the detailed molecular mechanisms of lncRNA KIAA0087 in OS remain obscure. Here, the roles of KIAA0087 in OS tumorigenesis were investigated. KIAA0087 and miR-411-3p levels were detected by RT-qPCR. Malignant properties were assessed by CCK-8, colony formation, flow cytometry, wound healing, and transwell assays. SOCS1, EMT, and JAK2/STAT3 pathway-related protein levels were measured by western blotting. Direct binding between miR-411-3p and KIAA0087/SOCS1 was validated by a dual-luciferase reporter, RIP, and FISH assays. In vivo growth and lung metastasis were evaluated in nude mice. The expression levels of SOCS1, Ki-67, E-cadherin, and N-cadherin in tumor tissues were measured by immunohistochemical staining. Downregulation of KIAA0087 and SOCS1 and upregulation of miR-411-3p were found in OS tissues and cells. Low expression of KIAA0087 was associated with a poor survival rate. Forced expression of KIAA0087 or miR-411-3p inhibition repressed the growth, migration, invasion, EMT, and activation of the JAK2/STAT3 pathway and triggered apoptosis of OS cells. However, the opposite results were found with KIAA0087 knockdown or miR-411-3p overexpression. Mechanistic experiments indicated that KIAA0087 enhanced SOCS1 expression to inactivate the JAK2/STAT3 pathway by sponging miR-411-3p. Rescue experiments revealed that the antitumor effects of KIAA0087 overexpression or miR-411-3p suppression were counteracted by miR-411-3p mimics or SOCS1 inhibition, respectively. Finally, in vivo tumor growth and lung metastasis were inhibited in KIAA0087-overexpressing or miR-411-3p-inhibited OS cells. In summary, the downregulation of KIAA0087 promotes the growth, metastasis, and EMT of OS by targeting the miR-411-3p-mediated SOCS1/JAK2/STAT3 pathway.