Introduction: This study compared the apical sealing ability of a bioceramic based root canalrepair filling material (iRoot FS) with mineral trioxide aggregate (MTA). Methods and materials: Forty single-canal teeth were prepared and randomly divided into two experimental groups (n=18) and two control groups (n=2). Teeth in experimental groups were retrofilled with either MTA or iRoot FS. After setting of the retrofillings, all roots were exposed to 0.2% Rhodamine B solution for 48 h and were then washed for 12 h before longitudinal sectioning. The extent of dye penetration was measured under fluorescence microscope. Results: The mean leakage values in MTA and iRoot FS samples were 35.63 and 35.15 µm, respectively. There was no significant differences between the two materials in this regard (P=0.584). Conclusion: According to dye leakage results, iRoot FS had similar apical sealing ability to MTA and might be considered as a promising root-end filling material.