Atrial functional mitral regurgitation (AFMR) is mitral regurgitation in patients with atrial fibrillation (AF), whose left atrium (LA) is enlarged, the left ventricle is not enlarged or only slightly enlarged, the left ventricular ejection fraction is preserved, and the mitral valve itself has no apparent lesion. At present, the etiology, pathophysiology and mechanism of this disease have not been completely clear yet. Existing studies have found that the causes of AFMR mainly include AF, enlargement of LA and mitral annulus, destruction of mitral annular shape, inability of mitral valve remodeling to compensate for mitral annular expansion, and hamstringing of the posterior mitral leaflet by atriogenic tethering. AFMR is demonstrated to be associated with an increased risk of mortality and readmission due to heart failure. Therefore, it serves as a primary therapeutic target for patients with heart failure and AF. However, the optimal treatment of AFMR still remains controversial. Therefore, this article will mainly expound the current definition, etiology, pathophysiological mechanism, treatment, and prognosis of AFMR.