Aims: The prognostic value of functional tricuspid valve regurgitation (TR) in patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension (CTEPH) remains undetermined. This study aims to quantify the prognostic role of TR during follow-up in relation to right ventricle (RV) dysfunction on clinical outcomes. Methods and Results: Patients from our prospective cohort study with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension were included. The primary endpoint was a composite of death or lung transplantation. The longitudinal evolution of TR and RV dysfunction were modelled with generalized mixed-effect models, which were inserted in a cox model under the joint-modelling framework in order to investigate the association of TR and RV dysfunction with the endpoint. In total, 120 patients were included (median age:59, females:62%), with a mean follow-up of 3.2±2.1 years. 31 patients reached the endpoint (2 transplant, 29 mortality). On average the probability of moderate-to-severe TR decreased during follow-up, whereas the probability of moderate-to-severe RV dysfunction remained stable over time. The cumulative effect of moderate-to-severe TR (hazard ratio: 1.01 95%CI[1.00-1.01],P<0.001) and moderate-to-severe RV dysfunction (hazard ratio: 1.01 95%CI[1.00-1.01],P<0.001) was associated with the composite endpoint in univariable joint-models. In a multivariable joint-model with both the evolutions of TR and RV dysfunction only TR remained a significant predictor (hazard ratio: 1.01 95%CI[1.00-1.01],P<0.001). Conclusion: Persistent moderate-to-severe tricuspid valve regurgitation during follow-up predicts adverse outcomes and might be a better predictor of lung transplantation and mortality compared to right ventricle dysfunction.