BACKGROUND AND AIMS: Severe tricuspid regurgitation (TR) alters ventricular interaction and left-sided filling dynamics. However, the longitudinal effects of transcatheter tricuspid edge-to-edge repair (T-TEER) on left atrial (LA) remodelling and diastolic physiology remain poorly characterized. We aimed to evaluate longitudinal changes in LA structure, function, and diastolic haemodynamics following T-TEER. METHODS: We studied 125 consecutive patients undergoing T-TEER within the TRI-FR trial and registry (median age 78 [73-81] years; 60.8% women; 73.6% atrial fibrillation). Comprehensive echocardiography was performed at baseline, pre-discharge, and at 6 and 12 months. Longitudinal changes in LA volume index (LAVI), peak atrial longitudinal strain (PALS), E/e' ratio, LA stiffness index (LASI), and forward flow indices were analysed using linear mixed-effects models. RESULTS: Left atrial volume index decreased immediately after T-TEER (estimated change -8.1 ml/m2; 95% CI -14.6 to -1.6; adjusted P = .033), but this reverse remodelling was not sustained at 12 months. In contrast, LA reservoir function deteriorated early and remained impaired throughout follow-up [PALS -1.2%; 95% confidence interval (CI) -2.0 to -0.3; adjusted P = .029]. Estimated LV filling pressure increased acutely (E/e' + 3.26; 95% CI 2.34-4.18; adjusted P < .001), while LASI remained elevated at 12 months (ratio 1.22; 95% CI 1.05-1.42; adjusted P = .016). Stroke volume index and cardiac index did not change significantly over time (P = .969 and P = .562, respectively). Early mitral regurgitation worsening occurred in 20% of patients but was transient and unrelated to changes in diastolic or forward-flow parameters. CONCLUSIONS: Transcatheter tricuspid edge-to-edge repair induces immediate anatomical LA unloading but does not restore LA mechanical function. Despite early reductions in LA volume, filling pressure surrogates increased, LA stiffness remained elevated, and forward flow did not improve. These findings demonstrate a dissociation between structural and functional remodelling after TR correction and highlight the importance of serial assessment of LA mechanics and diastolic physiology following T-TEER.