© 2018 Journal of Conservative Dentistry.Objectives: The specific objective of this in vitro study was to determine whether the current flowable resin composites can establish an effective seal in repairing noncarious amalgam margin defects. Material and Methods: A total of 30 freshly extracted caries-free human third molars were used for this investigation. Class I preparations with a standardized 160-μ marginal defect were made by condensing amalgam against a Mylar strip. Accelerated aging and corrosion protocols were then applied to simulate oral conditions. The prepared teeth were randomly divided into five groups (n = 6 per group) according to the repair material employed as follows: (1) no treatment (control); (2) self-adhering flowable resin composite (Vertise Flow); (3) flowable resin composite (Filtek Ultimate Flowable); (4) sonic-activated resin composite (SonicFill); and (5) self-adhesive cement (SmartCem2). Specimens were thermocycled again and then immersed in 5% methylene blue at 37°C for 24 h. For dye-leakage measurements, specimens were sliced longitudinally using a low-speed diamond disk. Results: The results indicated that the flowable resin composite material significantly reduced marginal microleakage compared to the control and SonicFill (P < 0.05). Conclusion: Current flowable resin composites were found to be adequate materials for repairing noncarious amalgam margin defects.