Background: In the intensive care unit (ICU), stress hyperglycemia is a relatively prevalent occurrence. It has a number of underlying reasons, including neuroendocrine and inflammatory abnormalities in critically sick patients, which promote insulin resistance and excessive hepatic glucose production. Objective: The aim of the present study was to detect the relation between corrected QT interval (QTc) and non-diabetic stress hyperglycemia in critically ill patients. Patients and methods: This cohort study included non-diabetic stress hyperglycemia that was conducted at ICU, Internal Medicine Department, Zagazig University Hospitals. These patients with stress hyperglycemia were further subdivided into two groups according to QT maxc Interval prolongation. Results: There was statistically non-significant relation between gender of patients and either QT prolongation (65.3% versus 64.6% in males and females respectively), QTII, QT max or QT maxc. There was statistically significant relation between QT prolongation and QT maxc (significantly higher in those with prolonged QT), QT max (significantly higher in those with prolonged QT). There was statistically non-significant relation between QT prolongation and QTII interval. There is statistically non-significant relation between QT prolongation and either LVEDD, LVESD, EF, DMR or EPSS Conclusion: Prolongation of QT maxc interval is frequent in critically ill patients during stress hyperglycemia. There was statistically significant relation between QT prolongation and APACHEII (significantly higher in prolonged QT interval).