Aim & Background: Postoperative pain is a multifactorial phenomenon, influenced by patient-related factors, tooth characteristics, and procedural aspects. This systematic review aims to identify and analyze the factors influencing the occurrence of postoperative pain following conventionnal endodontic treatments. Materials and Methods: The protocol was developed according to the guidelines established by the PRISMA statement. An electronic search was conducted in two databases, MEDLINE via PubMed and Web of Science, using the Boolean operator "AND" with the following MeSH terms: "root canal therapy" and "postoperative pain", as well as keywords including "root canal preparation", "endodontics," and "apical debris extrusion". A standardized data extraction grid was developed, and Risk of bias was assessed through the Cochrane Risk of Bias 2.0 tool. The review protocol was registered on PROSPERO (CRD420251027137). Results: Of the 72 initial articles, 11 clinical trials were included. The selected studies investigated various procedural variables, such as shaping kinematics, irrigation dynamics, and obturation technique. Postoperative pain was assessed using the Visual Analog Scale (VAS), Numerical Rating Scale (NRS), Verbal Rating Scale (VRS), and OHIP-14. Ten studies were rated as having a low risk of bias, and one showed moderate risk. Conclusion: Postoperative pain after root canal treatment is a multifactorial phenomenon influenced by various procedural parameters. Although some techniques, such as continuous rotation shaping, negative pressure irrigation, and adjunctive use of photodynamic therapy, appear to be associated with lower pain levels, the current evidence does not support a definitive superiority of one protocol over another. Further high-quality clinical trials are needed to standardize pain assessment and clarify the most effective strategies for minimizing postoperative discomfort. Clinical Significance: Postoperative endodontic pain is a multifacto