Fiber Bragg Gratings (FBG) have been regarded as one of the most promising local monitoring sensors and are widely deployed in civil infrastructures. In this chapter, those FBG-based sensors aiming at civil structures have been briefly presented, including direct packaged strain and temperature sensors, indirect sensors constructed using FBG as a sensing element, and FBG based smart civil structures. Specific issues concerning methods of effectively and correctly applying the FBG sensors to civil infrastructures have been discussed. Those issues involve sensor installation technique, strain transfer based error modification, and temperature compensation. Finally, more than ten case studies of critical infrastructures outfitted with FBG sensors have been reported. Both research and practical applications show that FBG sensors are now competitive with conventional electrical sensors in long-term structural health monitoring.