We investigated the influence of tricuspid regurgitation (TR) severity on the echocardiographic peak systolic transtricuspid pressure gradient (TRPG) and evaluated the usefulness of the peak early diastolic transpulmonary valve pressure gradient (PRPG) for estimating pulmonary artery (PA) pressure. In 55 consecutive right heart-catheterized patients, we measured the peak systolic right ventricular (RV)–right atrial (RA) pressure gradient (RV-RA_CATH), peak early diastolic PA-RV pressure gradient (PA-RV_CATH), and mean PA pressure (MPAP_CATH). Using echocardiography, we obtained the TRPG, PRPG, and an estimate of the mean PA pressure (EMPAP) as the sum of PRPG and the estimated RA pressure, and measured the vena contracta width of TR (VC_TR). The difference between the TRPG and RV-RA_CATH was significantly greater in the very severe TR group (VC_TR > 11 mm) than in the mild, moderate, and severe TR groups, and significantly greater in the severe TR group (7 < VC_TR ≤ 11 mm) than in the mild TR group. The overestimation of the pressure gradient >10 mmHg by TRPG was not seen in the mild or moderate TR groups, but was observed in the severe and very severe TR groups (22 and 83%, respectively). In the ROC analysis, EMPAP could distinguish patients with MPAP_CATH ≥ 25 mmHg with the area under the curve of 0.93, 100% sensitivity, and 87% specificity. In conclusion, TRPG frequently overestimated RV-RA_CATH when VC_TR was >11 mm and sometimes did when VC_TR was >7 mm, where EMPAP using PRPG was useful for estimating PA pressure.