Background: Because of limited accuracy of noninvasive tests, diastolic stress testing plays an important role in the diagnostic work-up of patients with heart failure with preserved ejection fraction (HFpEF). Exercise right heart catheterization is considered the gold standard and indicated when HFpEF is suspected but left ventricular filling pressures at rest are normal. However, performing exercise during right heart catheterization is not universally available. Here, we examined whether pulmonary capillary wedge pressure (PCWP) during a passive leg raise (PLR) could be used as simple and accurate method to diagnose or rule out occult-HFpEF. Methods: In our tertiary center for pulmonary hypertension and HFpEF, all patients who received a diagnostic right heart catheterization with PCWP-measurements at rest, PLR, and exercise were evaluated (2014–2020). The diagnostic value of PCWP PLR was compared with the gold standard (PCWP EXERCISE ). Cut-offs derived from our cohort were subsequently validated in an external cohort (N=74). Results: Thirty-nine non-HFpEF, 33 occult-HFpEF, and 37 manifest-HFpEF patients were included (N=109). In patients with normal PCWP REST (<15 mmHg), PCWP PLR significantly improved diagnostic accuracy compared with PCWP REST (AUC=0.82 versus 0.69, P =0.03). PCWP PLR ≥19 mmHg (24% of cases) had a specificity of 100% for diagnosing occult-HFpEF, irrespective of diuretic use. PCWP PLR ≥11 mmHg had a 100% sensitivity and negative predictive value for diagnosing occult-HFpEF. Both cut-offs retained a 100% specificity and 100% sensitivity in the external cohort. Absolute change in PCWP PLR or V-wave derived parameters had no incremental value in diagnosing occult-HFpEF. Conclusions: PCWP PLR is a simple and powerful tool that can help to diagnose or rule out occult-HFpEF.