Aim: The aim of this IN VITRO study was to examine and compare the apical micro-leakage of AH PLUS, MTA Fill, ZOE apex sealers in dry and moist root canals by dye penetration method using stereomicroscope. Materials and Methods: This experimental study was performed on 38 extracted teeth with single root canal. Hand protaper files were used for preparation of the canals. Root canals were filled with a single gutta-percha cone, using one of the three sealers, under dry and wet root canal conditions (6 teeth in each group) and one positive control group and one negative control group. Orifices were sealed with glue wax and all root surfaces were covered with nail polish except the positive control group. After ten days in 100% humidity, teeth were placed in methylene blue (pH7), and then were cut in longitudinal axis. Blue color permeability was measured by stereomicroscope in micrometers. Data were analyzed by factorial design. Results: Mean apical micro-leakage was significantly lower in the dry groups (P < 0.001). Minimum and maximum micro-leakage was seen in AH26 and ZOE, respectively. MTA Fillapex did not exhibit a significant difference in apical micro-leakage between dry and moist conditions (P > 0.05). Conclusion: AH26 provided the least apical micro-leakage under dry conditions while ZOE had the highest micro-leakage under moist conditions. MTA Fillapex provided acceptable apical seal regardless of moisture.