Poly(3-hexylthiophene)-stabilized gold nanorods (Au-NR@P3HT nanocomposites) have been facilely fabricated by incubating Au nanorods (NRs) with thiol-terminated P3HT to investigate the effects of Au NRs on the excited-state dynamics and photovoltaic performances of P3HT. The S-1 decay of Au-NR@P3HT nanocomposites is found to be slower than that of pristine P3HT, suggesting that the stretched-strand conformation of P3HT chains attached to Au NRs makes structural relaxation more difficult. The amplitude of T-1 absorption is much smaller in Au-NR@P3HT nanocomposites than in pristine P3HT, indicating that the intersystem crossing of S-1 excitons into T-1 excitons does not occur efficiently in Au-NR@P3HT nanocomposites due to the nonflexible character of aggregated P3HT chains. From the comparison of the performances of organic photovoltaic devices, we have found that the device with the 3 % embedding of Au-NR@P3HT nanocomposites into the P3HT matrix of the active layer shows significantly improved photovoltaic performances (27 % enhancement in the power conversion efficiency), suggesting that the surface-plasmon resonances of Au NRs enhance the dissociation as well as the generation of excitons highly.