Ternary heterostructured nanofibers (NFs) consisting of plasmonic noble metal nanoparticles (Au, Ag, or Pt NPs), graphitic carbon nitride nanosheets (g-C3N4 NSs), and TiO2 NPs were synthesized in situ via a facile electrospinning technique combined with a subsequent thermal oxidation/reduction process. The thermal-reduced plasmonic NPs with sizes from 5 to 10 nm are dispersed uniformly into the heterojunctions of the NFs that are formed by thermal oxidation etching of exfoliated g-C3N4 NSs in the electrospun TiO2 nanofibrous matrix, as evidenced by microscopic and electronic structure analyses. In comparison to single-component photocatalysts, such as g-C3N4 NSs or TiO2 NFs, these ternary heterostructures exhibit significantly high photocatalytic activity for H-2 evolution under simulated sunlight irradiation. The enhanced photoactivities are attributed to the strong photosynergistic effect between the surface plasmon resonance (SPR) and the heterojunction interface sensitization, which results in the improvement of charge-carrier generation and separation in the ternary heterostructured NFs. Further investigations indicate that coupling heterojunction sensitization on the g-C3N4/TiO2 interface with Ag SPR effects by plasmonic resonant energy transfer is the optimal strategy for synergistically improving the charge-carrier kinetics to achieve highly efficient photocatalytic H-2 evolution. It is believed that our present study offers a promising method for the rational integration of multi-component photocatalytic systems that can realize high photocatalytic performances for use in solar-to-fuel conversion.