Lead cesium perovskite nanocrystals have become ideal triplet sensitizers in photovoltaic and luminescent applications due to their high fluorescence quantum yield and quantum confinement effect. In this paper, three-monolayer CsPbBr₃ nanoplatelets (NPLs) were used as triplet donors to achieve efficient triplet energy transfer (TET) from NPLs to 1-naphthalene carboxylic acid (NCA). CsPbBr₃ NPLs were synthesized by ligand-assisted reprecipitation at room temperature. After binding with NCA, the steady-state fluorescence of NPLs was quenched substantially, the fluorescence lifetime was shortened from 6.743 ns to 0.995 ns, and the TET efficiency was as high as 85.3%. Compared with the large nanocubes, the quantum confinement is the key to obtain high-efficiency TET for CsPbBr₃-polycyclic aromatic hydrocarbons (CsPbBr₃-PAHs) complex system. The results indicate that CsPbBr₃ NPLs can be used as triplet sensitizers in the fields of photon upconversion, photocatalytic oxidation-reduction reaction and room temperature phosphorescence based on TET.