Background: Perioperative right ventricular (RV) dysfunction is a frequent complication of cardiac surgery linked to poor outcomes and may result from the loss of pericardial support. We investigated whether pericardial closure preserves early postoperative RV function. Methods: We compared patients with pericardial closure versus open pericardium. Co-primary endpoints were early postoperative RV longitudinal function by tricuspid annular plane systolic excursion (TAPSE) and tricuspid annular systolic velocity (TASV). Adjusted comparisons used analysis-of-covariance (postoperative value adjusted for baseline) with prespecified covariates (baseline outcome, LV global longitudinal strain, left-ventricular ejection fraction, LVEDVI, sex, procedure; cardiopulmonary bypass and cross-clamp times when available). Holm correction-controlled multiplicity across the co-primary endpoints. Sensitivity linear mixed-effects models (time × group) were performed. Results: Pericardial closure was associated with better early RV longitudinal function after multivariable adjustment. TAPSE: adjusted mean difference (AMD, Closed–Open) 1.531 mm (95% CI 0.130–2.931; p = 0.033). TASV: AMD 1.694 cm/s (95% CI 0.437–2.951; p = 0.009; Holm-adjusted p = 0.018). Sensitivity analyses yielded consistent estimates. Conclusions: Pericardial closure was independently associated with improved early RV longitudinal function. These adjusted findings address baseline LV imbalances and support considering closure to preserve RV performance; confirmation in prospective trials is warranted.