Objectives: The aim of this study was to evaluation the apical leakage at laser irradiation with diode laser (810nm). Methods: Twenty single root teeth were randomly divided into two equal groups; group I (GI): with laser irradiation and group II: without laser irradiation. After canal preparation, the samples were irradiated following the parameters: 1.5W; 30J; 96J/cm2, following all root canal extension with circular movement for 5-7 sec of GI. This procedures was reported four times, total exposure of 20sec. All the roots were obtured using gutta-percha and Endo-REZ sealer and immersed in 2% methylene blue dye solution for 72h at 37oC. After the samples were washed in water by 5 minutes and dried. Then, they were longitudinally bisected in the vestibulo-lingual direction. The apical linear leakage measured with the aid of a computer program Image Lab. Results: The results showed no statistical difference between groups (p<0.05) using Mann-Whitney test. Conclusions: It was concluded that laser irradiation did not decreased the marginal apical leakage, according the parameters used.