Nanotechnology invaded the science and stepped into dentistry in an attempt to improve material qualities and performance. However, the mechanism by which nanotechnology alters resin composite properties are not well explained. The aim of this work is to evaluate the effects of the nanofillers on selected mechanical and physical properties of visible light-activated dental resin composite restorative materials and to gain a better understanding of the mechanisms by which these nanofillers affect material properties which may have an impact on the clinical practice. One nano-filled resin composite was characterized in this study in comparison to two microhybrids and two nanohybrid resin composites. Nano-sized filler particles improved wear resistance and strength properties of resin composite materials. Therefore, nanofilled and nanohybrid resin composites can be used for anterior and posterior restorations where both wear resistance and strength are required for their durability. However, the form of the nanofillers is a significant factor for their effects and mechanism of actions on both mechanical and physical properties.