Naphthol isomers, including α-naphthol (α-NAP) and β-naphthol (β-NAP), are used widely in various fields and are harmful to the environment and human health. The qualitative and quantitative determination of naphthol isomers is therefore of great significance. Herein, β-cyclodextrin (β-CD)-platinum nanoparticles (Pt NPs)/graphene nanosheets (GNs) nanohybrids (β-CD-PtNPs/GNs) were prepared for the first time using a simple wet chemical method and characterized by atomic force microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and electrochemical methods, and then applied successfully in the ultrasensitive electrochemical detection of naphthol isomers. The results show that the oxidation peak currents of naphthol isomers obtained at the glassy carbon (GC) electrode modified with β-CD-PtNPs/GNs are much higher than those at the β-CD/GNs/GC, PtNPs/GNs/GC, GNs/GC, and bare GC electrodes. Additionally, compared with other electrochemical sensors developed previously, the proposed electrode results in improved detection limits of about one order of magnitude for α-NAP (0.23 nM) and three orders of magnitude for β -NAP (0.37 nM).