The root canal system is instrumented, disinfected, and obturated in a single visit using single-visit root canal therapy. The occurrence of post-endodontic pain is one of the most prevalent problems documented in single-visit root canal treatments. The goal of this study was to assess postoperative pain with manual, rotary, and reciprocating file systems, as well as two distinct irrigation methods: a side-vented needle and passive ultrasonic irrigation. A total of 120 patients were treated by a single operator using a single-visit root canal. Except for the third molars, all maxillary and mandibular molars were chosen. Each group was divided into 40 patients at random.Group 1 used hand K files with a step-back technique, group 2 used Pro Taper Next rotary files, and group 3 used Wave One Gold reciprocating files for cleaning and shaping. Each group was further divided into two subgroups, each consisting of 20 patients receiving side-vented needle irrigation and 20 patients receiving passive ultrasonic irrigation. Postoperative pain was measured using a numerical rating pain scale at 6, 12, 24, and 7 days.Patients in the hand file group reported the most discomfort, while those in the reciprocating file group. In endodontic therapy, choosing a reciprocating instrument rather than a rotary instrument or a hand file is linked to the lowest rate of postoperative pain. The use of a side-vented needle versus passive ultrasonic irrigation does not affect postoperative discomfort.