Purpose: Guidelines-directed medical therapy (GDMT) may benefit patients with heart failure (HF) reduced ejection fraction ((HFrEF, ≤40%), however, there are significant gaps between guidelines and real-world practices. The aim of this study was to evaluated prescribing adherence to the recommended GDMT in HFrEF patients using the global guideline adherence score. Method: A retrospective study among HFrEF patients at the National Heart Centre in Muscat, Oman, was conducted between 1st January and 30th June 2022. The optimum target doses were identified according to the 2021 European Society of Cardiology HF guidelines. Thus, for eligible patients, prescribing all indicated GDMT in doses ≥50% of the target dose is considered good adherence; the use of more than half of the medications in doses ≥50% of the target dose, moderate adherence; and the use of less than half the recommended medications and/or in doses <50% of target dose, poor adherence. Univariate statistics were used for the analysis. Results: The overall mean age of the cohort was 57 ±13.6 years with a predominance of male patients (70%; n=180). The overall prescribing adherence to guideline-recommended HF medications was 71% good, 22% moderate, and 7% poor. There was a significate association between the sub-optimal dose of GDMT and patients with hypertension (P=0.004), dilated cardiomyopathy (P=0.015), older age (P=0.004) and chronic kidney disease (P=0.001). Conclusion: Prescribing adherence to recommended GDMT in Oman is similar to that of international studies. Furthermore, sub-optimal GDMT titration was significantly associated with older age and comorbidity, suggesting that frailty perception may have an impact on GDMT titration.