© 2017 Elsevier Inc. Functional mitral regurgitation (FMR) is a common finding in patients with acute heart failure (AHF) and reduced left ventricular ejection fraction (heart failure and reduced ejection fraction [HFrEF]). However, its clinical impact remains unclear. We aimed to evaluate the association between the severity of FMR after clinical stabilization and short-term adverse outcomes after a hospitalization for AHF. We prospectively included 938 consecutive patients with HFrEF discharged after a hospitalization for AHF, after excluding those with organic valve disease, congenital heart disease, or aortic valve disease. FMR was assessed semiquantitatively by color Doppler analysis of the regurgitant jet area, and its severity was categorized as none or mild (grade 0 or 1), moderate (grade 2), or severe (grade 3 or 4). FMR was assessed at 120 ± 24 hours after admission. The primary end point was the composite of all-cause mortality and rehospitalization at 90 days. At discharge, 533 (56.8%), 253 (26.9%), and 152 (16.2%) patients showed none-mild, moderate, and severe FMR. At the 90-day follow-up, 161 patients (17.2%) either died (n = 49) or were readmitted (n = 112). Compared with patients with none or mild FMR, rates of the composite end point were higher for patients with moderate and severe FMRs (p <0.001). After the multivariable adjustment, those with moderate and severe FMRs had a significantly higher risk of reaching the end point (hazard ratio = 1.50, 95% confidence interval 1.04 to 2.17, p = 0.027; and hazard ratio = 1.63, 95% confidence interval 1.07 to 2.48, p = 0.023, respectively). In conclusion, FMR is a common finding in patients with HFrEF, and its presence, when moderate or severe, identifies a subgroup at higher risk of adverse clinical outcomes at short term.