Aim: The purpose of this study was to assess and compare microleakage of two novel bulk-fill resin composites with traditional incremental composites. Materials and Methods: Standardized conservative Class II cavities were made on 120 sound maxillary premolars having approximately 4 mm of width with 2 mm gingival extension below CEJ keeping all line angles round and cavosurface margins beveled. Samples were categorized into the group of three (n = 40), based on composites used; Smart Dentine Replacement (SDR), X Tra Fill, and Z350 XT. The prepared cavities were filled with respective composites to a depth of 4 mm. Post thermocycling, Specimens were absorbed in 0.5% methylene blue for 8 h and soaked in tap water for 12 h samples were later split in mesiodistal direction at the center of the composite restorations with diamond disc. A total of 240 samples were obtained. The samples were viewed with ×20. One-way ANOVA and post-hoc Bonferroni test were used to derive statistical data. Results: SDR demonstrated considerably less micro leakage in comparison with X-Tra fill composites. Significantly high microleakage was observed in the traditional composites (Z350 XT). Conclusion: Novel Bulk-fill resin composites exhibited better adaptability and less microleakage compared to traditional multilayer composites.