Background: The tricuspid valve is often called the "forgotten valve" or "lost valve," because it is relatively understudied relative to the other cardiac valves. Left-sided valvular heart diseases represent the most common cause of functional tricuspid regurgitation (FTR) and the reported prevalence reached 25% to 30%. Objective: The aim of the work is to give an attention to the problem of moderate functional tricuspid valve regurgitation with mitral valve replacement and includes revision of anatomy of tricuspid valve, pathophysiology, diagnosis and management of functional tricuspid valve regurgitation. Patients and Methods: In the present retrospective study, 30 randomly selected patients with moderate functional tricuspid valve regurgitation (grade 2) underwent mitral valve replacement for the first time at Al-Hussein University Hospital without repair of their moderate functional tricuspid regurgitation. The study was approved by the medical ethics committee of Al-Azhar University Hospitals and a written informed consent is obtained from all patients. Results: In the present study and according to the sex, the females (9) represent (30%) while males (21) were (70%). Their age ranged between 40-60 years with mean 48.40 ± 6.92. The Degree of TR was mild 15 (50.0%), moderate 6 (20.0%), severe 3 (10.0%) and Trivial 6 (20.0%) of Echo data after 6 months. Conclusion: Functional tricuspid regurgitation (TR) is commonly associated with mitral valve (MV) diseases and the presence of significant TR is reported to be an indicator of poor prognosis after the surgical correction of MV diseases.