Objective: This study aimed to assess the coronal-sealing ability of two different root canal obturation materials: gutta-percha with AH Plus and Resilon with Epiphany SE between radiated and nonirradiated groups. Materials and Methods: Fifty-six extracted premolar teeth were randomly divided into two main groups according to the presence or absence of radiotherapy. Specimens were divided into two equal groups. In the radiotherapy group, a total dose of 60 Gy was delivered with 1.8 Gy/d fractions, 5 days a week, for 35 days. The root canals were obturated with either gutta-percha/AH Plus or Resilon/Epiphany SE canal sealer. The samples were then evaluated for the coronal-sealing ability using a centrifuging dye penetration test at 3000 rpm for 5 min in a 2% Rhodamine B solution. The degree of dye penetration was evaluated with a stereomicroscope. Results: Although the sealing ability of both groups was not affected in radiotherapy, the coronal leakage values of Resilon/Epiphany SE slightly increased when radiation was applied (P > 0.05). Conclusion: Radiotherapy does not significantly affect the coronal-sealing ability of root canal obturation materials, gutta-percha/AH Plus and Resilon/Epiphany SE.