Background: Heart failure (HF) is associated with poor prognosis, high morbidity and mortality. The prognosis can be optimised by guideline adherence, which also can be used as a benchmark of quality of care. The purpose of this study was to evaluate differences in use of HF medication between Dutch HF clinics. Methods: The current analysis was part of a cross-sectional registry of 10,910 chronic HF patients at 34 Dutch outpatient clinics in the period of 2013 until 2016 (CHECK-HF), and focused on the differences in prescription rates between the participating clinics in patients with heart failure with reduced ejection fraction (HFrEF). Results: A total of 8,360 HFrEF patients were included with a mean age of 72.3 ± 11.8 years (ranging between 69.1 ± 11.9 and 76.6 ± 10.0 between the clinics), 63.9% were men (ranging between 54.3 and 78.1%), 27.3% were in New York Heart Association (NYHA) class III/IV (ranging between 8.8 and 62.1%) and the average estimated glomerular filtration rate (eGFR) was 59.6 ± 24.6 ml/min (ranging between 45.7 ± 23.5 and 97.1 ± 16.5). The prescription rates ranged from 58.9–97.4% for beta blockers (p < 0.01), 61.9–97.1% for renin-angiotensin system (RAS) inhibitors (p < 0.01), 29.9–86.8% for mineralocorticoid receptor antagonists (MRAs) (p < 0.01), 0.0–31.3% for ivabradine (p < 0.01) and 64.9–100.0% for diuretics (p < 0.01). Also, the percentage of patients who received the target dose differed significantly, 5.9–29.1% for beta blockers (p < 0.01), 18.4–56.1% for RAS inhibitors (p < 0.01) and 13.2–60.6% for MRAs (p < 0.01). Conclusions: The prescription rates and prescribed dosages of guideline-recommended medication differed significantly between HF outpatient clinics in the Netherlands, not fully explained by differences in patient profiles.