Obstetric care in Japan is organized in 3 levels and half of all deliveries are conducted at primary facilities without neonatal intensive care unit. We evaluated the predictive accuracy of the sFlt-1/PlGF ratio for the onset of preeclampsia and adverse outcomes in pregnant women with suspected preeclampsia at multiple facilities in Japan, including primary facilities. 356 pregnant women from 18 + 0 to 36 + 6 weeks of pregnancy were enrolled. 303 women were included in the final analysis. The negative predictive value for ruling out preeclampsia within 1 week using the cut-off value 38 was 98.4% (95% CI, 96.2-99.3) with a negative likelihood ratio of 0.22 (95% CI, 0.09-0.53). The positive predictive value for ruling in preeclampsia within 4 weeks using the cut-off value 38 was 48.2% (95% CI, 38.0-58.5). The positive predictive value using a cut-off value of 85 was 65.0% (95% CI, 44.1-81.4) with a positive likelihood ratio of 12.21 (95% CI, 5.20-28.80). The positive predictive value for prediction of adverse outcomes within 4 weeks using the cut-off value 38 was 64.8% (95% CI, 53.1-75.0). To clarify the accuracy of the test currently covered by insurance in Japan, we additionally conducted an analysis focusing on pregnant women between 18 + 0 and 35 + 6 weeks, yielding even higher accuracy. Pregnant women with sFlt-1/PlGF ratio >38 should be referred to a higher-level medical institution. The appropriate use of sFlt-1/PlGF supported by a robust collaboration between primary and tertiary care institutions may help to improve perinatal outcomes in Japan.