Preeclampsia (PE) is a pregnancy-specific disorder associated with hypertension and proteinuria. Since there is no proven method to treat PE, early prediction and accurate diagnosis are essential for appropriate management of the disease. Thus, reliable biomarkers for diagnosing PE need to be identified and evaluated. We analyzed serum-soluble factors and miRNAs in 92 patients with PE and an equal number of healthy controls to identify new useful biomarkers for PE. Serum miR-31-5p, miR-155-5p, and miR-214-3p levels were significantly elevated in these patients and highly correlated with clinical symptoms of hypertension and proteinuria, whereas the miR-1290-3p level was decreased. The increased miRNAs were upregulated in an NF-κB-dependent manner and suppressed endothelial nitric oxide synthase (eNOS) and placental growth factor (PlGF) expression. The level of each miRNA had greater than 90% diagnostic accuracy, which was further increased by analyzing its ratio relative to that of miR-1290-3p. Taken together, the ratios of miR-31-5p, miR-155-5p, or miR-214-3p to miR-1290-3p may serve as reliable diagnostic or prognostic tools for PE, thereby providing evidence that these miRNAs are promising mechanism-based targets for designing therapeutic and preventive strategies for the clinical management of PE.