Abstract: Carbon fiber-reinforced polymer (CFRP) composites have been widely used as structural materials due to excellent specific strength, specific modulus, fatigue resistance and corrosion resistance. However, delamination remains one of the major failure modes of CFRPs, significantly limiting their application. The structural design strategy based on interlayer toughening has been proved to be an effective method to solve this problem. By introducing toughening phases into the interlayer regions, the interlayer fracture toughness of CFRPs can be significantly improved. This paper reviews recent research progress on interlayer toughening strategies for CFRP, highlighting the effects of toughening methods on the mechanical performance of the composites. In particular, the review focuses on the advances in multiscale synergistic intrinsic and extrinsic toughening strategies, elucidating the toughening mechanisms at various scales and the synergistic effects between them. Finally, future prospects for interlayer toughening of CFRP are discussed.