Introduction: This study aimed to compare apical transportation during retreatment using ProTaper Universal retreatment (PTUR), Mtwo R and D-RaCe instruments in curved root canals.,Methods: 36 extracted mandibular molar teeth with curved mesiobuccal roots were selected. The teeth were embedded into acrylic blocks. The blocks were fixed on the experimental setup. After determining the working length (WL), mesiobuccal canals were prepared with ProTaper Universal rotary instruments to size F1 (20/0.06). After the obturation, the teeth were randomly divided into groups; the PTUR files were used as D1 (30/0.09) for coronal third and D2 (25/0.08) at WL. Mtwo R files, R1 (15/0.05) and R2 (25/0.05) were used at WL. D-RaCe files were used as DR1 (30/.10) in cervical third and DR2 (25/0.04) at WL. Image J analysis software was used to measure the apical transportation. Differences between the 3 groups were analyzed with a 1-way ANOVA or Kruskal-Wallis tests.,Results: There was no significant difference between groups in the apical transportation in either the mesiodistal (p = 0.166) or buccolingual (p = 0.518) direction. Among the 3 groups, the apical transportation was the greatest in the D-RaCe group.,Conclusions: It can be concluded that all retreatment systems caused a similar level of apical transportation.