Introduction: The incidence of immediate postobturation pain associated with 2 sealer techniques was compared and potential prognostic factors identified. Methods: Patients referred for endodontic treatment were recruited with informed consent. Root canals were debrided and teeth rendered asymptomatic before random allocation to receive TotalFill BC (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) or AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland). Patients blinded to the sealer reported their postobturation pain experience 1, 3, and 7 days after treatment. Blinded and calibrated assessors independently reviewed treatment quality, sealer extrusion, and radiographic data under standardized conditions. Results: One hundred sixty eligible patients (163 teeth, 95.3%) returned their pain diary. No postobturation pain difference was found between the 2 sealers (P .05), although the AH Plus sealer technique was significantly associated with extrusion beyond the apex (P < .05; odds ratio [OR] = 3.02; 95% confidence interval [CI], 1.39?6.57). Thirty-three (20.6%) patients reported pain on day 1 (median 1 = very mild pain), 16 (10.0%) on day 3 (median 1 = very mild pain), and 9 (5.6%) on day 7 (median 2 = mild pain). The prognostic factors were as follows: (1) moderate/severe preoperative pain (OR = 4.41; 95% CI, 1.42?13.76 on day 3 and OR = 5.16; 95% CI, 1.17?22.78 on day 7), (2) provoked preoperative pain (OR = 4.24; 95% CI, 1.40?12.78 on day 3 and OR = 5.35; 95% CI, 1.27?22.51 on day 7), (3) pulpless tooth (OR = 0.11; 95% CI, 0.02?0.57 on day 3), and (4) sonic activation during treatment (OR = 3.02; 95% CI, 1.39?6.57 on day 1 and OR = 3.01; 95% CI, 1.05?8.59 on day 3). Conclusions: There was no significant difference in pain experience between teeth filled using AH Plus or TotalFill BC Sealer 1, 3, and 7 days after obturation. Patient-and treatment-related factors could influence postobturation pain. (J Endod 2021;47:169?177.)