Objects: The aim of the study was to assess the effect of dentin surface pretreatment using silver nanoparticles and incorporating them into adhesive system on the microleakage of resin composite restorations. Also, preparation and characterization of the tested nanoparticles, evaluating the effect of aging on microleakage and Ultra-morpholigical examination of tooth-restoration interface using Environmental Scaning Electron Microscope (ESEM). Materials & methods: Standardized class V cavities with the dimentions of "3× 2 ×2 mm" were prepared on the buccal surface of 60 premolar teeth. Teeth were divided into three equal groups of 20 each, according to the treatment (A): group (A1) without dentin pretreatment (Control), group (A2) dentin pretreated by silver nanoparticles, group (A3) dentin was treated by Ag NPs incorporated in the adhesive system. Each group was divided into two subgroups of 10 teeth each according to the storage time (T) either after 24 hours (T1) or after 3 months (T2). The microleakage was tested using standardized dye penetration method. All data were statistically analyzed using ANOVA test. Result: totally it was found that Ag NPs incorporated in the adhesive system group recorded statistically non-significant (P>0.05) lowest leakage mean value followed by dentin pretreatment by silver nanoparticles while the group without dentin pretreatment recorded statistically non-significant (P>0.05) highest leakage mean value. Regardless to the tested treatment, it was found that twenty four hr.grouprecorded non-statistically significant (P<0.05) lower leakage mean value than threemonths.Regarding Group A1 (without dentin pretreatment) twenty four hr.grouprecorded lower leakage mean value than three months. The difference was statistically significant (p<0.05). Regarding Group A2 (dentin pretreatment by silver nanoparticles) twenty four hr.grouprecorded lower leakage mean value than three months. The difference was statistically significant (p<0.05).Regarding Group A3 (Ag NPs incorporated in the adhesive system) twenty four hr.grouprecorded lower leakage mean value than three months. The difference was statistically non-significant (p>0.05).Conclusion: Nanoparticles are influenced by features as their size, shape, peak of absorption and surface charge. Adhesive system incorporating spherical shape silver nanoparticles with 4-10 nm size and 3 μg/ml concentration in ethanol based solution positively reduced the leakage interface space of resin composite bonded to dentin that continues with aging. Dentin pretreated with silver nanoparticles had a limited role on the microleakage profile that deteriorates with aging. Silver nanoparticles are a promising antibacterial agent that didn’t antagonize penetration of resin tags into dentinal tubules and formation of hybrid layer.