OBJECTIVE To compare and evaluate microleakage at the occlusal wall and cervical wall in Class V cavities restored with Ivoclar Tetric N Ceram Bulk Fill composite, Tetric N Flow composite and N Ceram nanocomposite. METHODS Sixty-six extracted human maxillary premolars, which were intact and healthy, were randomly assigned into 3 groups (n=22). Standardized Class V cavities were prepared on the buccal surface of maxillary premolars. The occlusal walls of the cavities were located on the enamel and the cervical walls were located on dentin and cementum. After etching and application of the same bonding agents, the cavities were restored with different composite materials. Group A: Tetric N Ceram nano-hybrid composite , Group B: Tetric N Flow nano-hybrid composite, Group C: Tetric N Ceram Bulk Fill nano-hybrid composite. After curing with soft-start mode, finishing and polishing, the specimens were subjected to thermocycling. The specimens were coated with nail varnish, and immersed in 2% methylene blue solution for 7 days. The teeth were then sectioned longitudinally. Two of the samples chosen randomly from each group were evaluated under scanning electron microscope. Dye penetration of the remaining samples was examined with a stereomicroscope (×40) and scored separately for occlusal and gingival aspect on a 0-3 ordinal scale. The leakage depth was measured with Spot Advanced version 4.6 software package. The data were analyzed with Kruskal-Wallis, Mann-Whitney and Wilcoxon test using SPSS 17.0 software package. RESULTS Tetric Bulk Fill had significantly less microleakage at the cervical margins than other groups (P<0.05). There was no significant difference at the occlusal margin (P>0.05) between the three groups. There was significant difference between the enamel and cervical wall microleakage (P<0.05). CONCLUSIONS With the limitations of this study, Tetric Bulk Fill provided the least microleakage at the cervical wall among the three groups. There was no significant difference at the occlusal margin.