Objectives: Patients with heart failure (HF) and reduced left-ventricular ejection fraction (LVEF) benefit from angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blocker (ARB) therapy. While dose reduction/discontinuation (r/d) of β-blockers (BB) and furosemide in acute decompensated HF (ADHF) worsen outcomes, data on ACEI/ARB are lacking. Methods: To determine the frequency and reasons for ACEI/ARB therapy r/d in ADHF patients, we studied 174 patients with LVEF <40% on ACEI/ARB and BB therapy upon admission over 1 year. Results: ACEI/ARB doses were r/d in 17.2% because of acute kidney injury (56.7%), hypotension (23.3%), and hyperkalemia (10%). Clinical characteristics were similar between patients with r/d and continued therapy. Admission and discharge creatinine (Cr) levels were higher in the r/d group. On multivariate analysis, admission Cr and admission systolic blood pressures were independent predictors of r/d. Among patients with renal dysfunction cited as the r/d reason, Cr did not significantly rise in 23.5%. The r/d group had a longer length of stay (LOS). Conclusions: ACEI/ARB dose is reduced and/or discontinued in nearly one-fifth of all ADHF admissions, and LOS is longer in the ACEI/ARB r/d group. While impaired renal function is the most frequently cited reason, nearly one-fourth of the patients had stable renal function. ACEI/ARB r/d therapy in the setting of ADHF merits further study.