Objectives: The objective of this study investigated the relation between QT‑dispersion (QTd) and both number of coronary artery disease and major adverse cardiovascular events (MACEs) among patients with type 2 diabetes after elective percutaneous coronary intervention (PCI). Methods: One hundred ischemic heart disease patients undergoing elective coronary angioplasty were included; 49 patients with diabetes (group I) and 51 patients without diabetes mellitus (group II). Based on the QTd parameter after PCI, both groups were subdivided into tertiles. Angiographic, electrocardiographic parameters, and MACE were compared. Results: Both QTd after PCI and delta QTd were correlated to the number of diseased coronary arteries and MACE in patients with diabetes compared to patients without diabetes. QTd was longer in patients with diabetes developing MACE than those without MACE (r = −0.31, P = 0.04). Conclusion: QTd after PCI and delta QTd are the independent predictors of MACE in patients with type 2 diabetes.