Recently, Förster resonance energy transfer (FRET)‐based strategy has been successfully applied to promote the efficiencies of ternary blend organic solar cells (TOSCs). However, the intrinsic mechanism of FRET in the observed enhancement of efficiency has not been deconvolved unambiguously due to the complex photophysics mechanism. In this review, by deeply analyzing recent examples of FRET‐incorporated TOSCs, diverse framework structures of FRET pairs are summarized, then the theory, prerequisites, and the confirmation methods for FRET are discussed. In particular, the role of FRET theory in the photoconversion process is discussed in detail, including exciton harvesting, exciton diffusion, and charge generation. Finally, the existing challenges and future research directions of FRET applications in TOSCs are proposed.