Atrial secondary tricuspid regurgitation (A-STR) is a distinct phenotype of secondary tricuspid regurgitation characterized by predominant dilation of the right atrium and normal right and left ventricular function. It commonly occurs in elderly women with atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF). The main mechanism of leaflet malcoaptation in A-STR is the significant dilation of the tricuspid annulus due to right atrial enlargement, leading to an imbalance between the annulus and leaflets. Unlike ventricular secondary tricuspid regurgitation (V-STR), A-STR is typically associated with trivial tricuspid valve leaflet tethering. A-STR accounts for 10%–15% of clinically relevant tricuspid regurgitation and has better outcomes compared to V-STR. Recent data suggest that patients with A-STR may benefit from more aggressive rhythm control and timely valve interventions. However, current guidelines lack specific guidance on identifying, evaluating, and managing these patients due to the lack of consistent evidence and variable definitions. This expert opinion document aims to provide a standardized nomenclature and definition of A-STR, review its pathophysiology, diagnosis, and management, and highlight the need for further research to optimize treatment strategies. The document emphasizes the importance of early diagnosis and referral to specialized centers for A-STR patients, particularly those with severe symptoms or advanced disease.Atrial secondary tricuspid regurgitation (A-STR) is a distinct phenotype of secondary tricuspid regurgitation characterized by predominant dilation of the right atrium and normal right and left ventricular function. It commonly occurs in elderly women with atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF). The main mechanism of leaflet malcoaptation in A-STR is the significant dilation of the tricuspid annulus due to right atrial enlargement, leading to an imbalance between the annulus and leaflets. Unlike ventricular secondary tricuspid regurgitation (V-STR), A-STR is typically associated with trivial tricuspid valve leaflet tethering. A-STR accounts for 10%–15% of clinically relevant tricuspid regurgitation and has better outcomes compared to V-STR. Recent data suggest that patients with A-STR may benefit from more aggressive rhythm control and timely valve interventions. However, current guidelines lack specific guidance on identifying, evaluating, and managing these patients due to the lack of consistent evidence and variable definitions. This expert opinion document aims to provide a standardized nomenclature and definition of A-STR, review its pathophysiology, diagnosis, and management, and highlight the need for further research to optimize treatment strategies. The document emphasizes the importance of early diagnosis and referral to specialized centers for A-STR patients, particularly those with severe symptoms or advanced disease.