Post-obturation pain is one of the primary problems following root canal treatment. Although in most cases pain does not last long, but could be a source of embarrassment to the dentist and annoying for the patient. This study was conducted to investigate and compare the incidence of postoperative pain after one-visit root canal treatment (RCT) on teeth with vital pulps using three different obturation techniques. 90 cases were assigned into three treatment groups, each group 30 cases(10 anterior, 10 premolar, 10 molars), The canals of all teeth were prepared using Protaper rotary system and then filled at the same visit using one of the three obturation techniques (lateral condensation technique, HEROFILL technique, E&Q PLUS technique). The postoperative pain was recorded on a visual analogue scale (VAS) of 0 - 100 after 2 hours, 24 hours, 48 hours and 7 days.