Aim: To evaluateand compare the effect of different Nickel–Titanium system–Twisted File Adaptive (TFA), WaveOne and ProTaper Next (PTN) on canal transportation, centering ability and volumetric changes of mesiobuccalroot canal of mandibular molars via cone beam computed tomography (CBCT) imaging. Method: Mesiobuccal root canals of 30 mandibular molars with angle of curvature ranging from 10–20˚ were divided randomly into three groups of 10 each. Canals were prepared to a tip size 25 using TFA, WaveOne and PTN. Pre and post instrumentation scans were performed to compare canal transportation and centering ability at level of2mm, 5mm and 8mm from CEJusing 3D CBCT images. Volumetric changes were estimated by comparing the difference in volume of root canals recorded before and after instrumentation of canal. One way ANOVA was used to compare canal transportation, centering ratio and volumetric changes between groups. All statistical procedures were performed with significance level set at 5%. Results:The result demonstrated that Gp I (TFA) and Gp II (WO) showed statistically significant difference in canal transportation at all three levels. Gp I and Gp II showed significant difference at coronal level only. All file systems based on different kinematics remained well centered in canal at all levels. There was no significant difference in volumetric changes among three Ni–Ti file systems. Conclusion:PTN and TFN had similar results regarding canal transportation. WaveOne caused more canal transportation. All file system remain well centered. No significant difference in volumetric changes in root canals instrumented using three different Ni–Ti file systems.