Objective: To determine the microleakage at cervical third in three endodontic obturation techniques in diaphanized teeth. Materialsand Methods: 18 single root premolars were sectioned, instrumented and divided into four groups (n = 18) and sealed by techniquesusing: G1 ultrasound; G2 thermo-mechanical and G3 GuttaFlow®. The control group G Control (n = 3) without root filling, teeth weretrans-parented according to the Robertson technique. The samples were observed under an optical microscope at 4x using graphpaper. Comparison of groups was performed using the Kruskal-Wallis 95% confidence interval. Results: Group 2 with thethermomechanical technique showed lower microleakage, followed by Group 1 and Group 3. Conclusions: Three endodonticobturation techniques presented microleakage, being the thermo-mechanical technique the one that showed less microleakage. KIRU.2016;13(2):144-149.