Objectives <p>To assess the feasibility and accuracy of 4D flow MRI-based grading of left ventricular diastolic dysfunction, using echocardiography as the reference method.</p> Methods <p>Between October 2016 and February 2022, subjects were prospectively recruited for transthoracic echocardiographic evaluation of left ventricular diastolic function and 4D flow MRI at 3 T. Echocardiographic grading of diastolic dysfunction was performed according to the multiparametric, threshold-based 2016 ASE/EACVI approach. Volumetric and echo-equivalent peak velocity grading parameters were evaluated from 4D flow magnitude and velocity data, respectively. Duration of vortical blood flow along the main pulmonary artery (<i>t</i>_vortex) was employed as a surrogate grading parameter for echocardiographic tricuspid regurgitant peak velocity (TR). Correlations between grading parameters were analysed; agreement in grading of diastolic dysfunction between methods was assessed using a 5 × 5 contingency table analysis.</p> Results <p>The study population consisted of 94 participants (mean age, 62 ± 12 years, 50 females, 34 with structural heart disease). All volumetric and echo-equivalent 4D flow grading parameters demonstrated strong to very strong correlations with echocardiography (<i>r</i> = 0.75–0.92). Volumetric parameters showed significant biases between 4D flow and echocardiography. Employing bias-adjusted 4D flow grading cutoffs for volumetric parameter, echo-equivalent cutoffs for diastolic transmitral and myocardial peak velocities, and <i>t</i>_vortex &gt; 15% as a surrogate cutoff for TR &gt; 2.8 m/s, nearly perfect agreement in diastolic dysfunction grading between methods was observed (weighted kappa = 0.84). There was no evidence for over- or underestimation of grades by 4D flow (<i>p</i> = 0.53).</p> Conclusion <p>Grading of left ventricular diastolic dysfunction from a single 4D flow measurement is feasible and shows nearly perfect agreement with echocardiography.</p> Key Points <p><Emphasis Type="BoldItalic">Question</Emphasis> <i>The lack of comparison studies with echocardiography currently limits cardiac MRI-based grading of diastolic dysfunction. Could 4D flow MRI serve as a viable technique</i>?</p> <p><Emphasis Type="BoldItalic">Findings</Emphasis> <i>A single 4D flow MRI measurement allows multiparametric grading of left ventricular diastolic dysfunction in nearly perfect agreement with echocardiography</i>.</p> <p><Emphasis Type="BoldItalic">Clinical relevance</Emphasis> <i>Agreement between 4D flow MRI and echocardiographic grading of left ventricular diastolic dysfunction is comparable to that observed in repeated echocardiographic evaluations, suggesting 4D flow as a viable alternative to echocardiography in selected patients, especially when comprehensive MRI is already performed</i>.</p> Graphical Abstract <p></p>