The study aimed to evaluate the quality of the hybridlayer form by three different adhesive systems. Class Vcavities were prepared on the buccal surface of fourtyextracted human premolars. The prepared teeth wererandomly assigned into four groups according to theadhesive system and application mode. The systemswere: Optibond S (OS, total-etch); Optibond Versa (OV,two-bottles, self-etch); Single Bond Universal (SBU,one-bottle, self-etch) and Single Bond Universal withetchant (SBU + etchant). All cavities were restored withcomposite (Filtek Z350XT). The samples were sectioned,polished and pretreated to remove minerals, proteinand water prior to SEM evaluation. From the images,thickness of the hybrid layers was measured. Present ofresin tags and adaptation failure were also recorded. Thedata obtained were analyzed using ANOVA, Dunnett’sT3, Kruskal-Wallis and Mann-Whitney tests. OS groupshowed the highest average hybrid layer thickness (4.34µm), followed by SBU + etchant (3.06 µm), OV (1.91 µm)and SBU (0.95 µm). Both adhesive and cohesive failureswere observed in SBU group. Present of prominent resintags were seen in both OS and OV groups. In conclusion,all the investigated adhesive systems were able to performdistinguishable actions as shown in micro-morphologicalalteration and hybrid layer thickness. Two-bottles, selfetchadhesive (OV) was proven to produce negligibleadaptation failure compared to other adhesive systems inthe present study. Combined all-in-one adhesive (SBU)was found to render a superior bonding performance intotal-etch mode comparing to self-etch mode.