Background/Aim: Norepinephrine, first line adrenergic agent used in critically ill patients with septic shock status, may additionally exacerbate catecholamine toxicity and in certain circumstances may contribute to poorer clinical outcomes that mostly related to sinus tachycardia or tachyarrythmia.  Methods: A retrospective study was conducted between Jan 2018 to May 2021. New Onset Prolonged Sinus Tachycardia (NOPST) incidence was recorded if the HR increased by at least 20% from baseline and exceeded 100 bpm and it was correlated with the corresponding Norepinephrine infusion rate. The correlation between NOPST incidence and its corresponding NE infusion rate was statistically investigated by Spearman Correlation Test. The studied critically ill patients divided to either Non-Septic Shock Cohort (Group I) and Septic Shock Cohort (Group II). In addition to One Sample and Independent-T Tests, Chi Square Test was used for the non-parametric data. The ROC analysis was used to investigate the AUROC and the operational Cutoff Norepinephrine rate was picked by investigating the highest youden’s index. Results: The overall NOPST incidence for our 1638 eligible studied critically ill patients was assessed at 65.6% during an average of 14.08±4.06 days and  21.00±5.61 days of the ICU and overall hospital admission days, respectively, in which only ICU stay days was significantly lower in Non-Septic Shock Cohort compared to the Septic Shock Cohort [13.85±3.39 days vs 14.40±4.82 days]. The operating cut-off NE infusion rate to elicit NOPST was investigated at 11.3 mcg per min with sensitivity and specificity of 55.70%, 90.80%, respectively. Conclusion: Septic critically patients on Norepinephrine infusion have significantly higher risk of New Onset Prolonged Sinus Tachycardia (NOSPT) and significantly higher ICU admission days, especially if this infusion rate exceeding 11.5 mcg/min.