Aim: The aim of this in vitro study was to compare the effect of separated fragments from two different nickel titanium rotary instruments on microleakage of the root canal filling. Material and method: Extracted anterior teeth with single canal and straight roots were used. The teeth were divided into three groups. Group 1 and Group 3 (the control group) were shaped with ProTaper ® rotary nickel-titanium (NiTi) files; Group 2 was shaped with Revo-S ® rotary files. In Group 1, ProTaper ® F3 files and in Group 2, Revo-S ® 30/06 files, were broken in the apical one-third part of the root canals. All canals were obturated with gutta-percha and AH Plus sealer. After immersion in basic fuchsine stain solutions for 48 h, the roots were longitudinally sectioned. Digital photographs of the root sections were evaluated with image analysis software. Statistical analyses were performed with one way ANOVA and Tamhane test. Results: Microleakage of the control group was significantly less than Group 1 and Group 2. However, there was no statistically significant difference between the microleakage values of the groups separated ProTaper ® or Revo-S ® instruments. Conclusion: Separation of rotary NiTi instruments in the root canals negatively affected the apical seal of the root canal fillings, regardless of the instrument type. Keywords: ProTaper ® , Revo-S ® , fractured instrument, microleakage, dye leakage