Fiber reinforced polymer (FRP) composites are being utilized in a wide range of application areas in structural rehabilitations because these materials are less affected by corrosive environmental conditions and known to provide longer life with less maintenance. However, there are still some concerns about FRP strengthened reinforced concrete (RC) structures, such as the presence of near-surface defects. Currently limited data exists regarding this issue. The presence of near-surface defects in the form of delaminations between the fiber reinforced polymer (FRP) laminate and concrete substrate can significantly affect the structural integrity and stiffness of the structural section. These defects should be properly detected and accurately located to access if injection or replacement is warranted. The control and assessment of these defects still require improvements in detection techniques and standardization in these assessment methods. The latest advances in non-destructive evaluation (NDE) techniques including technologies in microwave, acousto-ultrasonic, impact-echo and thermography are providing promising results in detecting such defects and are discussed in further detail in this paper.