Background: Glyphosate has recently been used with increasing frequency in suicide attempts, so clinical toxicologists occasionally encounter cases of severe systemic toxicity. The purpose of this study was to identify the early predictive factors of patients at risk for mortality and the usefulness of the QTc interval for predicting mortality from glyphosate intoxication. Methods: This was a retrospective cohort study conducted from January 2005 to December 2012. A total of 153 patients with acute glyphosate ingestion were included. Data on the total population were retrospectively analyzed for their association with mortality using univariate and multiple logistic analyses. Results: The average age of the patients was 56 years (range, 19~93 years). Of the 153 patients, 19(12.4%) died. The most common abnormal ECG findings were prolonged QTc interval followed by intraventricular conduction delay and first degree AV block. Non-survivors had a significantly more prolonged QTc interval when compared to that of survivors (survivors 453.4±33.6 msec vs. non-survivors 542±32.0 msec, p<0.001). QTc interval and age were associated with a significantly increased risk of death in a multiple logistic regression. In a receiver operating curve analysis, the QTc interval had significant discriminatory power. Conclusion: Prolonged QTc interval seems to be a useful prognostic factor for mortality in patients intoxicated with glyphosate.