Purpose: to evaluate and compare the post-operative pain after the use of two different irrigation tips: a side-vented Max-i-Probe® and an end-vented needle, NaviTip, tips in one-visit root canal treatment after 4, 12, 24 and 48 hours utilizing a modified Visual Analogue Scale (VAS).Subjects and Methods: Thirty medically-free patients aged between 18-55 years with no sex predilection were included. Only vital mandibular posterior teeth were selected. Root canal treatment was completed in one visit. Patients were randomly assigned into either of two groups according to the needle used as follows: Group A: Max-i-Probe; Group B: NaviTip.After obturation, Post-operative pain was assessed using the modified visual analogue scale (VAS) pre-operatively, 4 hours, 12 hours, 24 hours and 48 hours after post- operative treatment. Results: showed that there was no statistically difference between the two groups regarding the demographic data, prevalence of pre-operative pain, after 4 hours, and 48 hours. On the other hand, there was a statistically significant difference between group A (Max-i-probe) and group B (NaviTip) in median modified VAS scores after12 hours and 24 hours with group B showing higher scores. Conclusion: NaviTip caused more post-operative pain than Max-i-Probe in case of vital teeth.