Purpose: The current investigation was carried out to estimate the influence of single and multiple NiTi rotary file systems on prevalence of postoperative pain following root canal instrumentation using mechanical or manual glide path techniques. Materials and methods: Forty participants with a sympotomatic irreversible pulpitis of mandibular molars were contributed in this randomized, controlled, clinical double blinded study. The participants were assigned into two main groups according to the gliding path system used then further subdivided into two subgroups according to the shaping system used. After access cavity preparation and working length determination, the glide path was prepared using either the PathFiles or the K-Files then the canal shaping was carried out using either the WaveOne Gold or ProTaper Next systems then the root canals were obturated. The postoperative pain was assessed by means of the modified visual analogue scale following 6, 12, 24, 48, 72 hours and 7 days then the data were collected and analyzed. Results: Postoperative pain was significantly higher after using the WaveOne Gold and the K-Files. Conclusions: Although all systems caused postoperative pain, the mechanical glide path along with the multi-file continuous rotational systems could be considered as a promising and reliable approach in preparing the root canals with less postoperative pain.