Abstract Background Acute paraquat poisoning has a high mortality rate. Several prognostic factors have been proposed to predict the mortality risk of paraquat-poisoned patients. However, these prognostic factors are complex and some require a laboratory. Corrected QT (QTc) has been used as a prognostic factor in several clinical conditions, such as acute organophosphate poisoning. In addition, the measurement can be obtained in a reasonable amount of time. Study Objectives This study's objective was to investigate whether QTc can predict mortality in paraquat-poisoned patients. Methods This was a retrospective study. Potential prognostic factors such as QTc, vital signs at admission, and certain biochemistry variables were analyzed with Cox regression analyses for their ability to predict a patient's survival from paraquat poisoning. Results Sixty acute paraquat-poisoned patients were admitted to the emergency department during the study period. The QTc of the survival group ranged from 0.35 to 0.48 s, whereas the nonsurvivor group ranged from 0.32 to 0.63 s. The nonsurvivor group contained a higher percentage of patients with QTc prolongation (≥0.45 s) compared with the survivor group (p = 0.04). The hazard ratio of QTc prolongation for a patient's death was found to be 2.47 (95% confidence interval [CI] 1.68–5.67) in patients with a lower potassium level (<3.2 mEq/L) and 3.71 (95% CI 1.53–8.97) in patients with a higher potassium level (≥3.2 mEq/L). In addition, hyperdynamic circulation was observed upon admission of these poisoned patients. Conclusion QTc prolongation is a useful prognostic factor for predicting death in acute paraquat-poisoned patients. Cardiovascular collapse may occur in some paraquat-poisoned patients. Physicians can use QTc as an indicator of a patient's severity of poisoning and mortality risk.