Esterification with maleic anhydride before mechanical treatments enabled wood to fibrillate into thin and uniform thick lignocellulose nanofibers. The esterification did not affect the crystal structure of the cellulose, and carboxyl groups introduced by the esterification facilitated the fibrillation of the wood. Moisture in the reaction system caused hydrolysis of some of the lignin and hemicellulose, thereby assisting the fibrillation. The esterification significantly reduced the number of passes through the disk mill required for the production of lignocellulose nanofibers with large specific surface areas. By using a high-pressure homogenizer, 97 wt % of the esterified wood was fibrillated into 3 nm thick lignocellulose nanofibers.