Introduction: This randomized clinical trial was conducted to evaluate and compare the post-operative pain after using two different irrigation tips; end-vented NaviTip tip and double side-port NaviTip tip immediate postoperatively and at 4, 12, 24, 48, 72 hours and 7 days utilizing a numerical rating scale (NRS).Materials and methods: Thirty eight patients diagnosed with irreversible pulpitis in mandibular posterior teeth without periapical radiolucency were randomly assigned and underwent one-visit root canal treatment, Root canals were prepared using NiTi ProTaper Universal rotary system. Canals were then randomized into two equal groups according to the needle used for irrigation, group A (control) NaviTip® 29-gauge 27 mm with End vented Tip and Group B (intervention) NaviTip® 31-gauge 27 mm with double Side vented Irrigator Tip , The needles of irrigation were penetrated 2 mm shorter from the working length. Postoperative pain was recorded using NRS (no pain, mild, moderate and sever) immediately and at different follow up periods as previously mentioned and statistically analyzed. The intake of the given placebo capsule and the prescribed analgesics tablets were also recorded.Results:There was no statistically difference between the two groups regarding the demographic data, prevalence of pre-operative pain and postoperative pain intensity and incidence at 4 hours, 12 hours, 24 hours, 48 hours and 7 days. There was no statistically significance difference between two groups regarding the placebo and analgesics tablets intake.Conclusion: There is no statistical significance difference between End vented NaviTip and double side-port NaviTip regarding postoperative pain. In both groups there was a statistically significant decrease in pain intensity preoperatively compared with all other time periods.