Background: Limited research has been conducted to investigate the impact of secondary mitral regurgitation (MR) in heart failure (HF) patients with different levels of estimated pulmonary artery systolic pressure (ePASP). Methods: A total of 468 patients suffering from HF and secondary MR were enrolled and categorized into non-severe and severe MR groups based on the degree of MR. The primary endpoint of the study was a composite of cardiovascular death and a first-heart-failure hospitalization. The secondary endpoints were the primary outcomes, individually. The outcomes of the two groups were compared. Patients were further classified based on whether their ePASP was \ge50 mmHg or 50 mmHg. Subsequently, the outcomes of the non-severe and severe MR groups were compared within each ePASP category. Results: In a median (SD) follow-up of 694 (410) days, severe MR was associated with higher risk for primary endpoints in patients with heart failure, especially in those with ePASP \ge50 mmHg. In patients with ePASP 50 mmHg, the prognostic value of severe MR was diminished. Conclusions: Assessment of the severity of MR can identify heart failure patients who are at greater risks for poor clinical outcomes. Additionally, the prognostic value of secondary MR was more pronounced in patients with elevated ePASP.