Background: Heart failure (HF) patients with diabetes (DM) have an adverse prognosis and reduced functional capacity, which could be associated with cardiac fibrosis, increased chamber stiffness and reduced left ventricular (LV) contractile reserve. Galectin-3 (Gal-3) and fibulin-1 are circulating biomarkers potentially reflecting cardiac fibrosis. We hypothesize that plasma levels of Gal-3 and fibulin-1 are elevated in HF patients with DM and are associated with reduced LV contractile reserve in these patients. Methods: A total of 155 patients with HF with reduced ejection fraction underwent a low-dose dobutamine echocardiography and blood sampling for biomarker measurements. Patients were classified according to history of DM and an oral glucose tolerance test (OGTT) as: normal glucose tolerance (NGT) (n = 70), impaired glucose tolerance (IGT) (n = 25) and DM (n = 60). Results: Galectin-3 levels were elevated in DM patients as compared to non-diabetic patients (P = 0.02), while higher fibulin-1 levels were observed in HF patients with IGF and DM (P = 0.07). Reduced LV contractile reserve was associated with increasing Gal-3 levels (β = -0.19, P = 0.03) although, this association was attenuated after adjustment for estimated glomerular filtration rate (P = 0.66). Fibulin-1 was not associated with LV contractile reserve (P = 0.71). Conclusions: Galectin-3 and fibulin-1 levels were elevated in HF patients with impaired glucose metabolism. However, reduced LV contractile reserve among HF patients with DM does not to have an independent impact on plasma Gal-3 and fibulin-1 levels.