Chirality is ubiquitous in nature. Chiral plasmonic nanoparticles, which possess chiral features on their surfaces, have recently attracted much attention. They exhibit much stronger chiroptical responses than chiral molecules because of their larger sizes and localized surface plasmon resonances. We have developed seed-mediated recipes for the synthesis of chiral Au nanoparticles. The growth with Au nanodisks gives chiral Au nanotriskelions and helicoid Au nanocrystals. The average scattering dissymmetry factors of the L- and D-nanotriskelions reach +0.57 and −0.49 at 650 nm, respectively. The growth with Au nanodecahedrons gives chiral Au nanorods. We have further demonstrated the use of the chiral Au nanoparticles to realize circularly polarized organic light-emitting devices (CP-OLEDs). Efficient CP-OLEDs are realized through the assembly of chiral plasmonic Au nanoparticles and supramolecular aggregates. The chiral plasmonic nanoparticles serve as the chiral scaffold and chiral optical nanoantenna to modulate the circularly polarized absorption and emission of the supramolecular chromophores. The emissions of the OLEDs are dominated by either chiral excitons or chiral plasmons, dependning on the type of chiral plasmonic nanoparticle. The CP-OLED showing a high external quantum efficiency of 2.5% and a large dis-symmetry factor of 0.31 is achieved, as a result of multiscale chirality transfer, plasmonic enhancement, and the suppression of the overshoot effect. Previously reported CP-OLEDs generally exhibit an inverse relationship between the external quantum efficiency and the dis-symmetry factor. The CP-OLEDs fabricated in our work can achieve both high external quantum efficiencies and high dis-symmetry factors. The external quantum efficiencies of our devices are about two orders of magnitude higher than those of lanthanide-complex-based devices and the dis-symmetry factors are about two orders of magnitude larger than those of chiral cluster-based devices.