Using fiber-reinforced polymer (FRP) composites to increase the flexural strength of existing structures has gained wide acceptance in recent years. Using high-strength and high-quality adhesives, FRP laminates are externally bonded to the structure that has to be strengthened. Many experimental investigations and practical applications have been performed, thereby demonstrating that the strengthening effects can be reflected in a wide range of aspects, such as the enhancement of the structural stiffness, load-carrying capacity, ductility, and corrosion resistance. In this chapter, a clear understanding of the different failure mechanisms and influencing factors on the flexural performance of FRP-strengthened structures under monotonic and fatigue loads is developed. Based on a series of in-depth studies on the flexural performance of FRP-strengthened concrete structures, a rational methodology is established for the flexural design of FRP-strengthened concrete structures. Some attempts are also made to enhance the structural performance for FRP flexural strengthening. In addition, a series of special field applications for typical FRP flexural strengthening are introduced.