Background and aim 4Low-grade inflammation plays an important role in type-2 diabetes and coronary-artery disease pathogenesis. YKL-40 is expressed in cells of innate immunity and is associated with endothelial dysfunction. The research aims to see if YKL-40 levels in the blood could be used as a diagnostic biomarker in type-2 diabetic patients. Additionally, to evaluate if there is a link between YKL-40 and ischemic heart disease in diabetic patients. Patients and methods The study was carried out on 75 Egyptian individuals (25 healthy persons as control, 25 type-2 diabetic patients without ischemic heart disease, and 25 type-2 diabetic patients with ischemic heart disease). Enzyme-linked immunosorbent assay was used to assess YKL-40 levels. Results There was a significant elevation in the levels of YKL-40 when patients with type-2 diabetes mellitus (T2DM) uncomplicated by ischemic heart disease and patients with T2DM complicated by ischemic heart disease compared with the control group (P<0.05). The optimal YKL-40 cutoff threshold was greater than 65 ng/ml. Furthermore, the level of YKL-40 was significantly higher (P<0.05) in patients with T2DM complicated by ischemic heart disease compared with individuals with T2DM not complicated by ischemic heart disease. The best cutoff point for YKL-40 to differentiate between those two groups was greater than 110 ng/ml. Conclusion In type-2 diabetic patients, YKL-40 could be a valuable diagnostic marker for vascular complications.