BACKGROUND Early metastasis of osteosarcoma (OS) is highly lethal and responds poorly to drug and radiation therapies. MicroRNAs (miRNAs) are a class of small noncoding RNAs that modulate gene expression at the post-transcriptional level. However, the detailed functions of specific miRNAs are not entirely understood. The aim of the present study was to investigate the role of miR-184 as a mediator of drug resistance in human osteosarcoma. MATERIAL AND METHODS qRT-PCR was used to analyze the expression level of miR-184 in OS cell line U-2 OS and MG-63 treated with doxorubicin. MiR-184 agomir or miR-184 antagomir was transferred into cells to regulated miR-184. The target of miR-184 was predicted by TargetScan and confirmed by luciferase reporter assay. Bcl-2-like protein 1 (BCL2L1) expression was detected by Western blot. Cell apoptosis was determined by Annexin V staining and analysis by flow cytometry. RESULTS Doxorubicin induced time-dependent expression of miR-184 in OS cell line U-2 OS and MG-63. Luciferase reporter assay identified BCL2L1 as the direct target gene of miR-184. Furthermore, doxorubicin reduced BCL2L1 expression, which was reversed by miR-184 overexpression and further decreased by miR-184 inhibition in OS cells. In addition, miR-184 agomir reduced doxorubicin-induced cell apoptosis, whereas miR-184 antagomir enhanced apoptosis in OS cells, suggesting that up-regulation of miR-184 contributes to chemoresistance of the OS cell line. CONCLUSIONS Our data show that miR-184 was up-regulated in OS patients treated with doxorubicin therapy and leads to poor response to drug therapy by targeting BCL2L1.