This study aimed to determine mean pulmonary arterial pressure (PAPmean) and pulmonary vascular resistance (PVR) using transthoracic echocardiography (TTE) measurements of the pulmonary artery flow velocity curve in children with pulmonary arterial hypertension (PAH) and congenital heart disease when the tricuspid regurgitant velocity (TRV) is not sufficient. This study enrolled 29 congenital heart disease cases with pulmonary arterial hypertension and 40 healthy subjects followed at our center. The mean age was 66.9 ± 77.9 months in the patient group and 76.3 ± 62.1 months in the control group. A positive correlation was found between TRV and systolic pulmonary arterial pressure (r = 0.394, p = 0.035, 95% confidence interval [CI] = 0.032-0.665), whereas a negative correlation was found between corrected acceleration time (AcTc) and PAPmean (r = -0.559, p = 0.002, 95% CI = -0.768 to -0.242). Furthermore, a negative correlation was found between parameters TRV and AcTc (r = -0.383, p = 0.001, 95% CI = -0.657 to -0.019). Based on the cutoff criterion of 124 ms for AcTc, sensitivity was found to be 79.3% and specificity to be 77.5% in distinguishing between the PAH patients and the healthy control patients (receiver operating characteristic [ROC] area under the curve [AUC] = 0.804, 95% CI = 0.691-0.890, p < 0.0001). The sensitivity and specificity of the concomitant use of AcTc and/or TRV were found to be 90 and 73%, respectively, in distinguishing between the PAH patients and the the healthy control patients. The data obtained by TTE also can be appropriate for measuring PAPmean, PVR, and the vasoreactivity test and for determining the priority of implementing cardiac catheterization even if there is no measurable TRV value.