A nanodiamond particle dispersion including nanodiamond particles highly dispersed in an organic solvent is provided. A nanodiamond particle dispersion of the present invention includes nanodiamond particles dispersed in an organic solvent, in which the nanodiamond particles have a silane compound (excluding a silane compound having a (meth)acryloyl group) bonded to a surface of the nanodiamond particles, the organic solvent has an SP value from 8.0 to 14.0 (cal/cm3)1/2, and the nanodiamond particles are dispersed with a particle diameter (D50) from 2 to 100 nm. The organic solvent is preferably at least one type of organic solvent selected from ketones, ethers, alcohols, and carbonates.