Objectives Right ventricular (RV) function is an important prognostic marker in heart failure. However, its impact on all-cause mortality following cardiac resynchronisation therapy (CRT) independent of confounding factors has not been evaluated. Furthermore, evidence concerning the effect of CRT on RV function is limited. The study's aims were to: (1) assess the prognostic importance of RV function among CRT recipients, and (2) characterise RV functional change following CRT and its determinants. Design Retrospective observational study. Setting Single tertiary centre. Patients A total of 848 CRT recipients (median age 65 years, 78% male, 60% ischaemic) underwent echocardiography before and 6 months after CRT. RV function was evaluated using tricuspid annular plane systolic excursion (TAPSE), with a ≤14 mm threshold indicating severe RV impairment. The primary endpoint was long-term all-cause mortality. Results Significant baseline RV dysfunction was observed in 286 (34%) individuals. After a median 44 months, 288 deaths occurred. RV impairment was associated with a greater incidence of all-cause mortality (log-rank p<0.001). Independent predictors of this endpoint were functional class, ischaemic aetiology, diabetes, atrial fibrillation, renal dysfunction, bigger left ventricular (LV) end-systolic volume, less LV dyssynchrony and reduced TAPSE. Importantly, TAPSE added prognostic value to these recognised prognostic parameters (likelihood-ratio test p<0.001). Furthermore, improvement in RV function after CRT was independent of the improvement in LV systolic function but significantly associated with the improvement in LV diastolic function. Importantly, a favourable RV functional response to CRT was associated with superior survival. Conclusions RV function is an independent predictor of long-term outcome following CRT.