BACKGROUND : Osteosarcoma (OS) is the most common malignant bone tumor in young adults and adolescents with approximately 3 million new cases annually. Due to the lack of sensitive and specific diagnostic biomarkers, although OS patients are curable after surgical resection, many patients suffer from metastasis or recurrence. This study aimed to investigate whether circulating microRNAs (miRNAs) could serve as biomarkers for the diagnosis of OS. METHODS : Healthy individuals and OS patients enrolled in this study came from Nanjing First Hospital. First, candidate miRNAs were selected by integrated analysis of two GEO datasets and a publicly available miRNA dataset. The expression of these miRNAs in tissues and serum samples were subsequently examined through qRT-PCR. The diagnostic utility of these differential miRNAs was examined by using receiver operating characteristic (ROC) curve analysis. Finally, the potential signaling pathways associated with candidate miRNAs were searched through online tools. RESULTS : Four miRNAs (miR-487a, miR-493-5p, miR-501-3p and miR-502-5p) were selected to further investigate their diagnostic potential for OS. We discovered miR-487a, miR-493-5p, miR-501-3p and miR-502-5p were upregulated in OS tissues and serums. Besides, miR-487a, miR-493-5p, miR-501-3p and miR-502-5p in peripheral blood of OS patients were tumor-derived. The area under the ROC curve (AUC) was 0.83 (95% CI 0.71-0.97) for miR-487a, 0.79 (95% CI 0.66-0.93) for miR-493-5p, 0.82 (95% CI 0.68-0.95) for miR-501-3p, 0.83 (95% CI 0.72-0.95) for miR-502-5p, and 0.89 (95% CI 0.78-1.0) for miRNAs combination. CONCLUSIONS : Circulating miR-487a, miR-493-5p, miR-501-3p and miR-502-5p were novel potential diagnostic biomarkers of OS.