This study aimed to report on the use, predictors and outcomes of guideline-based medical therapy (GBMT) in patients with acute heart failure (HF) with reduced ejection fraction of <40% (HFrEF), from seven countries in the Arabian Gulf.Patients with acute HFrEF (N = 2680), aged 18 years or older, and hospitalized February-November 2012 were recruited and data were collected post discharge at 3 months (n = 2477) and 1 year (n = 2418). The use and doses of GBMT were evaluated as per European, American and Canadian HF guidelines. Analyses were performed using multivariate logistic regression. This study was registered at clinicaltrials.gov (NCT01467973).The majority of patients were on dual (39%) and triple (39%) GBMT modalities, 14% received one GBMT medication, while 7.2% were not on any GBMT medications. On admission, 80% of patients were on renin-angiotensin system (RAS) blockers, 75% on b-blockers and 56% on mineralocorticoid receptor antagonists (MRAs), with a small proportion of these patients were taking target doses (RAS blockers 13%, b-blockers 7.3%, MRAs 14%). Patients taking triple GBMT were younger (P