The aim of this study was to investigate the effect of esterification via acetic or propionic anhydride on the surface roughness of eastern cottonwood. Eastern cottonwood (Populous deltoides) was esterified by using acetic or propionic anhydride without using any solvent or catalyst under different conditions. Two different weight percentage gains (WPGs) were obtained for each of the modifying chemicals. Three main surface roughness parameters, namely average roughness (Ra), mean peak to valley height (Rz) and maximum roughess (Rmax) were measured by a stylus method before and after esterification. The surface roughness was significantly increased due to the esterifications. The surface roughness of wood increased with increasing WPG.