In this study, cholesterol sensors consisting of a mixture of cholesterol oxidase (ChOx) and zinc oxide (ZnO) nanoparticles (NPs) are constructed on plastic substrates and their sensing characteristics are examined in air. The current of the ChOx-ZnO NP film decreases in magnitude as cholesterol molecules are adsorbed on the film, due to the resulting increase in the number of electrons generated by the reaction between the cholesterol and the ChOx. The cholesterol sensor shows a high sensitivity of $1.08{mu}A/mM$ and a wide detection range from 10 nM to 1 mM.